The noun mission has 5 senses (first 4 from tagged texts)
1. (18) mission, missionary post, missionary station, foreign mission -- (an organization of missionaries in a foreign land sent to carry on religious work)
2. (8) mission, military mission -- (an operation that is assigned by a higher headquarters; "the planes were on a bombing mission")
3. (8) mission, charge, commission -- (a special assignment that is given to a person or group; "a confidential mission to London"; "his charge was deliver a message")
4. (7) mission, missionary work -- (the organized work of a religious missionary)
5. deputation, commission, delegation, delegacy, mission -- (a group of representatives or delegates)