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.
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   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