A term expressing an expectation of reciprocity. If event A happens, then event B will certainly follow. Most commonly used in the phrase "mutually assured destruction," which posits that the best defense against a nuclear-based attack is the threat of a "mutually assured" retaliatory nuclear-based attack...although the term can be applied to events less earth-shakingly catastrophic.
"If I go down on you, it damn well better be mutually assured that you'll be sucking my cock afterwards."
by lexicographer September 15, 2003