n. & int.
n. (pl. -ies) 1 compassion or forbearance shown to enemies or offenders in one's power. 2 the quality of compassion. 3 an act of mercy. 4 (attrib.) administered or performed out of mercy or pity for a suffering person (mercy killing). 5 something to be thankful for (small mercies).
int. expressing surprise or fear. at the mercy of 1 wholly in the power of. 2 liable to danger or harm from. have mercy on (or upon) show mercy to. mercy flight the transporting by air of an injured or sick person from a remote area to a hospital.
[ ME f. OF merci f. L merces -edis reward, in LL pity, thanks ]