From 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]
From WordNet (r) 3.0 (2006) :
somnambulation
n 1: walking by a person who is asleep [syn: sleepwalking,
somnambulism, somnambulation, noctambulism,
noctambulation]