The Collaborative International Dictionary of English v.0.48:

Sleepwalking \Sleep"walk`ing\, n.
   Walking in one's sleep.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Somnambulation \Som*nam`bu*la"tion\, n. [L. somnus sleep +
   ambulatio a walking about, from ambulare to walk. See
   Somnolent, Amble.]
   The act of walking in sleep, called also sleepwalking.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sleepwalking
    n 1: walking by a person who is asleep [syn: sleepwalking,
         somnambulism, somnambulation, noctambulism,
         noctambulation]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "sleepwalking":
   amnesia, beauty sleep, beddy-bye, bedtime, blanket drill, bye-bye,
   catalepsy, cataplexy, catatonic stupor, daydreaming, daze, doze,
   dream state, dreamland, drowse, fitful sleep, fugue, fugue state,
   hibernation, hypnotic trance, land of Nod, light sleep,
   night-wandering, nightwalking, noctambulation, noctambulism,
   noctivagation, repose, reverie, shut-eye, silken repose, sleep,
   sleepland, sleepwalk, slumber, slumberland, snoozle, somnambulant,
   somnambulism, somniloquy, somnus, stupor, trance, unconsciousness,
   winter sleep