The Collaborative International Dictionary of English v.0.48:

Straiten \Strait"en\, v. t. [imp. & p. p. Straitened; p. pr. &
   vb. n. Straitening.]
   1. To make strait; to make narrow; hence, to contract; to
      confine.
      [1913 Webster]

            Waters, when straitened, as at the falls of bridges,
            give a roaring noise.                 --Bacon.
      [1913 Webster]

            In narrow circuit, straitened by a foe. --Milton.
      [1913 Webster]

   2. To make tense, or tight; to tighten.
      [1913 Webster]

            They straiten at each end the cord.   --Pope.
      [1913 Webster]

   3. To restrict; to distress or embarrass in respect of means
      or conditions of life; -- used chiefly in the past
      participle; -- as, a man straitened in his circumstances.
      [1913 Webster]

WordNet (r) 3.0 (2006):

straiten
    v 1: bring into difficulties or distress, especially financial
         hardship [syn: straiten, distress]
    2: squeeze together

Moby Thesaurus II by Grady Ward, 1.0:

81 Moby Thesaurus words for "straiten":
   arrest, bottle up, bound, box in, box up, bridle, cabin, casket,
   check, cloister, closet, coffin, condition, confine, constrain,
   constrict, contain, contract, control, cool, cool off, copyright,
   cramp, crib, curb, curtail, decelerate, diminish, discipline,
   dompt, draw in, draw the line, encase, enjoin, entomb, go in,
   govern, guard, hedge about, hinder, hold, hold at bay, hold back,
   hold fast, hold in, hold in check, hold in leash, hold up, immure,
   inhibit, keep, keep back, keep from, keep in, keep in check,
   keep under control, lay under restraint, limit, moderate, narrow,
   patent, prohibit, pull, pull in, qualify, register, rein, rein in,
   restrain, restrict, retard, retrench, scant, set back, slow down,
   snape, snub, specialize, stint, taper, withhold