Source : Webster's Revised Unabridged Dictionary (1913)

Sigh \Sigh\, v. i. [imp. & p. p. {Sighed}; p. pr. & vb. n.
   {Sighing}.] [OE. sighen, si?en; cf. also OE. siken, AS.
   s[=i]can, and OE. sighten, si?ten, sichten, AS. siccettan;
   all, perhaps, of imitative origin.]
   1. To inhale a larger quantity of air than usual, and
      immediately expel it; to make a deep single audible
      respiration, especially as the result or involuntary
      expression of fatigue, exhaustion, grief, sorrow, or the
      like.

   2. Hence, to lament; to grieve.

            He sighed deeply in his spirit.       --Mark viii.
                                                  12.

   3. To make a sound like sighing.

            And the coming wind did roar more loud, And the
            sails did sigh like sedge.            --Coleridge.

            The winter winds are wearily sighing. --Tennyson.

   Note: An extraordinary pronunciation of this word as s[=i]th
         is still heard in England and among the illiterate in
         the United States.