Source : Webster's Revised Unabridged Dictionary (1913)

Drowse \Drowse\, v. i. [imp. & p. p. {Drowsed}; p. pr. & vb. n.
   {Drowsing}.] [AS. dr?sian, dr?san, to sink, become slow or
   inactive; cf. OD. droosen to be sleepy, fall asleep, LG.
   dr?sen, druusken, to slumber, fall down with a noise; prob,
   akin to AS. dre['o]san to fall. See {Dreary}.]
   To sleep imperfectly or unsoundly; to slumber; to be heavy
   with sleepiness; to doze. ``He drowsed upon his couch.''
   --South.

         In the pool drowsed the cattle up to their knees.
                                                  --Lowell.

Drowse \Drowse\, v. t.
   To make heavy with sleepiness or imperfect sleep; to make
   dull or stupid. --Milton.

Drowse \Drowse\, n.
   A slight or imperfect sleep; a doze.

         But smiled on in a drowse of ecstasy.    --Mrs.
                                                  Browning.

Source : WordNet®

drowse
     n : a light fitful sleep [syn: {doze}]

drowse
     v 1: sleep lightly or for a short period of time [syn: {snooze},
          {doze}]
     2: be on the verge of sleeping; "The students were drowsing in
        the 8 AM class"