The noun formation has 7 senses (first 6 from tagged texts)
1. (7) formation -- (an arrangement of people or things acting as a unit; "a defensive formation"; "a formation of planes")
2. (4) formation -- (a particular spatial arrangement)
3. (4) formation, shaping -- (the fabrication of something in a particular shape)
4. (4) constitution, establishment, formation, organization, organisation -- (the act of forming something; "the constitution of a PTA group last year"; "it was the establishment of his reputation"; "he still remembers the organization of the club")
5. (3) geological formation, formation -- ((geology) the geological features of the earth)
6. (1) formation -- (natural process that causes something to form; "the formation of gas in the intestine"; "the formation of crystals"; "the formation of pseudopods")
7. formation -- (creation by mental activity; "the formation of sentences"; "the formation of memories")