Source : Webster's Revised Unabridged Dictionary (1913)

Straighten \Straight"en\, v. t. [imp. & p. p. {Straighted}; p.
   pr. & vb. n. {Straighting}.]
   1. To make straight; to reduce from a crooked to a straight
      form.

   2. To make right or correct; to reduce to order; as, to
      straighten one's affairs; to straighten an account.

   {To straighten one's face}, to cease laughing or smiling,
      etc., and compose one's features.