A linguistic phenomenon whereby a word constitutes its own antonym depending on context. English, being widely spoken and/or occasionally mangled in the United States and recalcitrant parts of the commonwealth (i.
e., Canada), features many enantiosemic
words, including inflammable, nonplussed, and restive (with the latter meaning "impatient and fidgety" when applied to
people and, owing to its
French roots, "stubbornly refusing to move" when applied to horses).
From Gr. enantios ("opposite") + semasia ("meaning").
Gord: HOW DO MOUNTIES MANAGE TO BE NONPLUSSED ALL THE
TIME, ANYWAY? THERE ARE GUYS WITH RACCOONS IN THEIR JACKETS AND STUFF—
Nigel: Actually, its prefix notwithstanding, and despite plussed's non-status as a word, "nonplussed" means the opposite of what it's commonly thought to mean.
Gord, nonplussed: OKAY, SO WE'RE TALKING ENANTIOSEMY, BUT LOOK, THE
HORSE IS RESTIVE, AREN'T YA,
BUD?
RCMP Thoroughbred: <snorts and offers an impregnable stare>
Inflammable means flammable? What a country! What enantiosemy!
―
Dr. Nick Riviera, whose doctorate is in linguistics, not medicine