Union  n. 1 uniting or being united. 2 a whole formed from parts or members. B political unit so formed. 3 = *trade union. 4 marriage. 5 concord (perfect union). 6 (union) a university social club and (at oxbridge) debating society. B buildings of this. 7 math. Totality of the members of two or more sets. 8  mixed fabric, e.g. Cotton with linen or silk. [latin unus one]