disjunctive conjunction

GNU Webster's 1913

1. adj. (Gram.) one connecting grammatically two words or clauses, expressing at the same time an opposition or separation inherent in the notions or thoughts; as, either, or, neither, nor, but, although, except, lest, etc.

WordNet 3.0

1. n. the conjunctive relation of units that expresses the disjunction of their meanings