nocturnal penile tumescence

Sexology The spontaneous erection of the penis during sleep occurring from birth to advanced old age, typically, 3 episodes/night, for a total of 2-3 hrs (!!!); NPT occurs during REM sleep and is accompanied by erotosexual dreams. See Postage stamp test.

McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.