(v.) To unite by compact, as sovereignties, states, or nations; to join in confederacy; to league\.

act in concert act together affiliate ally amalgamate associate band band together be in cahoots be in league bunch bunch up cabal cement a union centralize club club together coact coalesce collaborate collude combine come together concert concord concur confederate consociate consolidate conspire cooperate couple do business with federalize fuse gang gang up get heads together get together go in partners go in partnership go partners hang together harmonize hold together hook up hook up with join join forces join fortunes with join in join together join up with join with keep together league league together make common cause marry merge organize pair pair off partner play ball pull together put heads together reciprocate stand together stand up with team up team up with team with throw in together throw in with tie in tie in with tie up tie up with unionize unite unite efforts unite with wed work together