Definition of "somnambulist"

The clergyman floundered a moment, as is usual with an absent man who is recovering the train of his ideas, or a somnambulist when he is suddenly awakened.

1824, Sir Walter Scott, chapter 17, in St. Ronan's Well

The slim one got up and walked straight at me - still knitting with downcast eyes - and only just as I began to think of getting out of her way, as you would for a somnambulist, stood still, and looked up.

1899 February, Joseph Conrad, “The Heart of Darkness”, in Blackwood’s Edinburgh Magazine, volume CLXV, number M, New York, N.Y.: The Leonard Scott Publishing Company, […], part I, page 199

He must have promptly rejected an alternative explanation which would better fulfill the demands of verisimilitude (“My wife, poor thing, in her nervous condition, now is afflicted also with sleepwalking!”), seeing the laborious tasks to which the resumed somnambulist devotes herself: kneeling at the edge of a pit, she anoints the earth with murky philters (unless the implements she holds in her hand are to be interpreted actually as acetylene torches scattering sparks, to melt the lead seals of a coffin).

1977, William Weaver (translator), Italo Calvino (author), The Castle of Crossed Destinies (first published 1969), part 2, chapter 5, 1969