The Collaborative International Dictionary of English v.0.48:

Plague \Plague\, n. [L. plaga a blow, stroke, plague; akin to
   Gr. ?, fr. ? to strike; cf. L. plangere to strike, beat. Cf.
   Plaint.]
   1. That which smites, wounds, or troubles; a blow; a
      calamity; any afflictive evil or torment; a great trail or
      vexation. --Shak.
      [1913 Webster]

            And men blasphemed God for the plague of hail.
                                                  --Wyclif.
      [1913 Webster]

            The different plague of each calamity. --Shak.
      [1913 Webster]

   2. (Med.) An acute malignant contagious fever, that often
      prevails in Egypt, Syria, and Turkey, and has at times
      visited the large cities of Europe with frightful
      mortality; hence, any pestilence; as, the great London
      plague. "A plague upon the people fell." --Tennyson.
      [1913 Webster]

   Cattle plague. See Rinderpest.

   Plague mark, Plague spot, a spot or mark of the plague;
      hence, a token of something incurable.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Plague \Plague\, v. t. [imp. & p. p. Plagued; p. pr. & vb. n.
   Plaguing.]
   1. To infest or afflict with disease, calamity, or natural
      evil of any kind.
      [1913 Webster]

            Thus were they plagued
            And worn with famine.                 --Milton.
      [1913 Webster]

   2. Fig.: To vex; to tease; to harass.
      [1913 Webster]

            She will plague the man that loves her most.
                                                  --Spenser.
      [1913 Webster]

   Syn: To vex; torment; distress; afflict; harass; annoy;
        tease; tantalize; trouble; molest; embarrass; perplex.
        [1913 Webster]

WordNet (r) 3.0 (2006):

plague
    n 1: a serious (sometimes fatal) infection of rodents caused by
         Yersinia pestis and accidentally transmitted to humans by
         the bite of a flea that has bitten an infected animal [syn:
         plague, pestilence, pest, pestis]
    2: any epidemic disease with a high death rate [syn: plague,
       pestilence, pest]
    3: a swarm of insects that attack plants; "a plague of
       grasshoppers" [syn: infestation, plague]
    4: any large scale calamity (especially when thought to be sent
       by God)
    5: an annoyance; "those children are a damn plague"
    v 1: cause to suffer a blight; "Too much rain may blight the
         garden with mold" [syn: blight, plague]
    2: annoy continually or chronically; "He is known to harry his
       staff when he is overworked"; "This man harasses his female
       co-workers" [syn: harass, hassle, harry, chivy,
       chivvy, chevy, chevvy, beset, plague, molest,
       provoke]

Moby Thesaurus II by Grady Ward, 1.0:

181 Moby Thesaurus words for "plague":
   afflict, affliction, aggravate, aggravation, ail,
   ambulatory plague, anguish, annoy, annoyance, apply pressure,
   badger, bait, bane, be at, be the matter, bedevil, beleaguer,
   beset, besiege, bevy, bitch, black death, black plague, blandish,
   blight, bother, bristle, brown off, bubonic plague, bug, bugbear,
   bullyrag, burden, burn up, buttonhole, cajole, calamity,
   cellulocutaneous plague, chafe, charm, chevy, chivy, cloud, coax,
   complicate matters, concern, covey, crawl with, creep with,
   crushing burden, curse, death, defervescing plague, destruction,
   devil, discommode, discompose, disease, distemper, distress,
   disturb, dog, drag, dun, epidemic, epiphytotic, epizootic, evil,
   exasperate, exercise, exert pressure, fash, flight, flock, fret,
   gaggle, gall, get, glandular plague, gnaw, grievance, gripe,
   harass, harm, harry, hassle, haunt, headache, heckle, hector,
   hemorrhagic plague, hive, hound, importune, inconvenience, infest,
   infestation, infliction, invade, invasion, irk, irritate,
   irritation, larval plague, lousiness, miff, molest, murmuration,
   murrain, nag, nag at, needle, nemesis, nettle, nudzh, nuisance,
   open wound, overrun, overrunning, overspread, overspreading,
   overswarm, overswarming, pandemia, pandemic, peeve, perplex,
   persecute, perturb, pest, pester, pesthole, pestilence, pick on,
   pique, plague spot, pluck the beard, ply, pneumonic plague, pother,
   premonitory plague, press, pressure, provoke, push, put out,
   put to it, puzzle, ravage, ride, rile, roil, ruffle, running sore,
   scourge, septicemic plague, siderating plague, skein, spring,
   swarm, swarm with, swarming, tease, teeming, thorn, torment,
   torture, trouble, try the patience, tuberculosis, tweak the nose,
   urge, vex, vexation, visitation, watch, wheedle, white plague, woe,
   work on, worry



Easton's 1897 Bible Dictionary:

Plague
   a "stroke" of affliction, or disease. Sent as a divine
   chastisement (Num. 11:33; 14:37; 16:46-49; 2 Sam. 24:21).
   Painful afflictions or diseases, (Lev. 13:3, 5, 30; 1 Kings
   8:37), or severe calamity (Mark 5:29; Luke 7:21), or the
   judgment of God, so called (Ex. 9:14). Plagues of Egypt were ten
   in number.

     (1.) The river Nile was turned into blood, and the fish died,
   and the river stank, so that the Egyptians loathed to drink of
   the river (Ex. 7:14-25).

     (2.) The plague of frogs (Ex. 8:1-15).

     (3.) The plague of lice (Heb. kinnim, properly gnats or
   mosquitoes; comp. Ps. 78:45; 105:31), "out of the dust of the
   land" (Ex. 8:16-19).

     (4.) The plague of flies (Heb. arob, rendered by the LXX.
   dog-fly), Ex. 8:21-24.

     (5.) The murrain (Ex.9:1-7), or epidemic pestilence which
   carried off vast numbers of cattle in the field. Warning was
   given of its coming.

     (6.) The sixth plague, of "boils and blains," like the third,
   was sent without warning (Ex.9:8-12). It is called (Deut. 28:27)
   "the botch of Egypt," A.V.; but in R.V., "the boil of Egypt."
   "The magicians could not stand before Moses" because of it.

     (7.) The plague of hail, with fire and thunder (Ex. 9:13-33).
   Warning was given of its coming. (Comp. Ps. 18:13; 105:32, 33).

     (8.) The plague of locusts, which covered the whole face of
   the earth, so that the land was darkened with them (Ex.
   10:12-15). The Hebrew name of this insect, _arbeh_, points to
   the "multitudinous" character of this visitation. Warning was
   given before this plague came.

     (9.) After a short interval the plague of darkness succeeded
   that of the locusts; and it came without any special warning
   (Ex. 10:21-29). The darkness covered "all the land of Egypt" to
   such an extent that "they saw not one another." It did not,
   however, extend to the land of Goshen.

     (10.) The last and most fearful of these plagues was the death
   of the first-born of man and of beast (Ex. 11:4, 5; 12:29,30).
   The exact time of the visitation was announced, "about
   midnight", which would add to the horror of the infliction. Its
   extent also is specified, from the first-born of the king to the
   first-born of the humblest slave, and all the first-born of
   beasts. But from this plague the Hebrews were completely
   exempted. The Lord "put a difference" between them and the
   Egyptians. (See PASSOVER.)


The Devil's Dictionary (1881-1906):

PLAGUE, n.  In ancient times a general punishment of the innocent for
admonition of their ruler, as in the familiar instance of Pharaoh the
Immune.  The plague as we of to-day have the happiness to know it is
merely Nature's fortuitous manifestation of her purposeless
objectionableness.