noun.
The act of subsiding from a swollen state, especially the relaxation of an erect penis.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
noun.
diminution of swelling; the subsidence of anything swollen
Word Usage
"In the past, it had always ended with Billy's orgasm, followed by detumescence, a poorly aimed kiss near the ear, a slipping away into stertorous sleep."