The Collaborative International Dictionary
Retrocopulation
Retrocopulation \Re`tro*cop`u*la"tion\, n. [Pref. retro- +
copulation.]
Copulation from behind.
--Sir T. Browne.
Douglas Harper's Etymology Dictionary
retrocopulation
"copulation from behind," 1640s, from retro- + copulation. Related: Retrocopulate (v.).
Wiktionary
retrocopulation
n. copulation from behind.