The Oxford Thesaurus An A-Z Dictionary of Synonyms - occasionaladj.

1) intermittent, irregular, periodic, random, sporadic, infrequent, casual, incidental: They staged occasional raids on the arsenal. He works as an occasional farm hand. 2) additional, extra, spare, supplementary, incidental, auxiliary, accessory: We bought a few occasional chairs in case we have company. 3) special, particular, ceremonial, ritual: She writes occasional verses for memorial services.