Learner's definition of MISSION
1 a : a task or job that someone is given to do
b : a specific military or naval task c : a flight by an aircraft or spacecraft to perform a specific task
Our mission was to recover the stolen plans.
He was sent on a fact-finding mission. = He was sent on a mission to gather information.
By patient negotiation she succeeded in her mission of averting a strike.
go on a rescue mission [=go somewhere to rescue someone]
The volunteers were on a mission of mercy to help victims of the disaster. [=the volunteers were sent to help the victims of the disaster]
a mercy mission
a bombing mission
a manned space mission
a shuttle mission
a mission to the moon
2 : a task that you consider to be a very important duty
His mission is to help poor children. = He has made it his mission in life to help poor children. = He's a man with a mission: to help poor children.
She's on a mission to locate her lost sister. [=she is very determined to find her lost sister]
3 : a group of people sent to a foreign country for a specific reason (such as to have discussions or to provide training or assistance) 4 a : a group of people who are sent to a foreign country to do religious work : a group of missionaries b : a place or building where such work is done