The Collaborative International Dictionary of English v.0.48:

Substitute \Sub"stit"ute\, n. [L. substitutus, p. p. of
   substituere to put under, put in the place of; sub under +
   statuere to put, place: cf. F. substitut. See Statute.]
   One who, or that which, is substituted or put in the place of
   another; one who acts for another; that which stands in lieu
   of something else; specifically (Mil.), a person who enlists
   for military service in the place of a conscript or drafted
   man.
   [1913 Webster]

         Hast thou not made me here thy substitute? --Milton.
   [1913 Webster]

         Ladies [in Shakespeare's age] . . . wore masks as the
         sole substitute known to our ancestors for the modern
         parasol.                                 --De Quincey.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Substitute \Sub"stit"ute\, v. t. [imp. & p. p. Substituted; p.
   pr. & vb. n. Substituting.] [See Substitute, n.]
   To put in the place of another person or thing; to exchange.
   [1913 Webster]

         Some few verses are inserted or substituted in the room
         of others.                               --Congreve.
   [1913 Webster]

WordNet (r) 3.0 (2006):

substitute
    adj 1: capable of substituting in any of several positions on a
           team; "a utility infielder" [syn: utility(a),
           substitute(a)]
    2: serving or used in place of another; "an alternative plan"
       [syn: alternate, alternative, substitute]
    3: artificial and inferior; "ersatz coffee"; "substitute coffee"
       [syn: ersatz, substitute]
    n 1: a person or thing that takes or can take the place of
         another [syn: substitute, replacement]
    2: an athlete who plays only when a starter on the team is
       replaced [syn: substitute, reserve, second-stringer]
    3: someone who takes the place of another (as when things get
       dangerous or difficult); "the star had a stand-in for
       dangerous scenes"; "we need extra employees for summer fill-
       ins" [syn: stand-in, substitute, relief, reliever,
       backup, backup man, fill-in]
    v 1: put in the place of another; switch seemingly equivalent
         items; "the con artist replaced the original with a fake
         Rembrandt"; "substitute regular milk with fat-free milk";
         "synonyms can be interchanged without a changing the
         context's meaning" [syn: substitute, replace,
         interchange, exchange]
    2: be a substitute; "The young teacher had to substitute for the
       sick colleague"; "The skim milk substitutes for cream--we are
       on a strict diet" [syn: substitute, sub, stand in,
       fill in]
    3: act as a substitute; "She stood in for the soprano who
       suffered from a cold" [syn: substitute, deputize,
       deputise, step in]

Moby Thesaurus II by Grady Ward, 1.0:

148 Moby Thesaurus words for "substitute":
   additional, advocate, agent, alter ego, alternate, alternative,
   amicus curiae, analogy, another, attorney, backup, backup man,
   bit player, champion, change, change for, changeling, commute,
   comparison, compound for, copy, counterfeit, delegate, deputy,
   dernier ressort, displace, double, double for, dub in, dummy,
   equal, equivalent, ersatz, exchange, executive officer, expediency,
   expedient, exponent, extra, fake, false, father figure,
   father image, figurant, figurante, figurehead, fill-in, ghost,
   ghostwriter, give place to, imitation, lieutenant, locum,
   locum tenens, make do with, make way for, makeshift, metaphor,
   metonymy, mock, mother figure, mother surrogate, mute,
   next best thing, offer in exchange, other, paranymph, personnel,
   phony, pinch, pinch hitter, pinch-hit for, pleader, procurator,
   provisional, proxy, put up with, recourse, redeem, refuge, relay,
   relief, relieve, replace, replacement, representative, reserve,
   reserves, resort, ring in, ringer, second, second in command,
   second string, secondary, sham, shift with, sign, simulated, spare,
   spares, spear-carrier, spurious, stand in for, stand-in, standby,
   stopgap, sub, substituent, substitute for, substitution,
   succedaneum, supe, super, supernumerary, superseder, supplant,
   supplanter, supplemental, supplementary, supply, support,
   supporting actor, supporting cast, surrogate, swap, switch, symbol,
   synecdoche, take in exchange, temporary, tentative, third string,
   token, trade, understudy, utility, utility man, utility player,
   vicar, vicar general, vicarious, vice, vice-president, vice-regent,
   vicegerent, walk-on, walking gentleman



The Free On-line Dictionary of Computing (30 December 2018):

Substitute
SUB

    (SUB) ASCII character 26.

   [Why?]

   (1996-06-28)


Bouvier's Law Dictionary, Revised 6th Ed (1856):

SUBSTITUTE, contracts. One placed under another to transact business for
him; in letters of attorney, power is generally given to the attorney to
nominate and appoint a substitute.
     2. Without such power, the authority given to one person cannot in
general be delegated to another, because it is a personal trust and
confidence, and is not therefore transmissible. The authority is given to
him to exercise his judgment and discretion, and it cannot be said that the
trust and confidence reposed in him shall be exercised at the discretion of
another. 2 Atk. 88; 2 Ves. 645. But an authority may be delegated to
another, when the attorney has express power to do so. Bunb. 166; T. Jones,
110. See Story, Ag. Sec. 13, 14. When a man is drawn in the militia, he may
in some cases hire a substitute.