noun

• (archaic) One in a state of magnetic or mesmeric sleep; someone in a hypnotic trance.
  "Though the sleepwalker sat with closely bandaged and wadded eyes, and his back to the grimacing part of the company, he described everything they were doing with the most comic humour, and he asked, 'What in the world is that gentleman in the chair making such faces for, and what is he giving himself such trouble about? […]""
• (figurative) One who goes though life in a state of obliviousness.
  "Perhaps he should have killed the white man, who, after all, is the dangerous one, the sleepwalker, the blind man . Getting rid of him would have protected " the higher interests of society " on three counts : It would have made this dreamer and sleepwalker "pay the price" for refusing to awaken to the truth of human identity; it would have destroyed the dreamer's "dream world," which excludes blacks; and it would have carried out the narrator's " responsibility," as "invisible victim," for " the fate of all"—for those both within and without the sleepwalker's dream world."