get together

a small informal social gathering; "there was an informal meeting in my living room"

get people together; "assemble your colleagues"; "get together all those who are interested in the project"; "gather the close family members"

get together socially or for a specific purpose

work together on a common enterprise of project; "The soprano and the pianist did not get together very well"; "We joined forces with another research group"

become part of; become a member of a group or organization; "He joined the Communist Party as a young man"