compassion or forbearance shown esp to an offender or an enemy
a fortunate circumstance
It was a mercy they found her before she froze
(used before a noun) giving or bringing help and relief to people in distress
a mercy flight
a mercy mission
at the mercy of
wholly in the power of (somebody or something)
[Middle English via Old French merci from Latin merced-, merces price paid, wages, from merc-, merx merchandise]