To attach at the end; subjoin; affix: as, to annex a codicil to a will.To unite, as a smaller thing to a greater; join; make an integral part of: as, to annex a conquered province to a kingdom.To attach, especially as an attribute, a condition, or a consequence: as, to annex a penalty to a prohibition.Synonyms Add, Affix, Attach. See add and list under affix.n. Something annexed; specifically, a subsidiary building connected with an industrial exhibition; hence, any similar arrangement for the purpose of providing additional accommodation, or for carrying out some object subordinate to the main and original object. Also spelled annexe.