Synonyms for disappointing

unsatisfactory, unsatisfying, ineffective, uninteresting, discouraging, unpleasant, inadequate, inferior, unlooked for, lame, insufficient, failing, falling short, limited, second-rate, mediocre, unexpected, unhappy, depressing, disconcerting, disagreeable, irritating, vexing, disheartening, unlucky, bitter, distasteful, displeasing, deplorable, short of expectations, frustrating, unfulfilling; see also inadequate 1, unsatisfactory.

Antonyms pleasing*, encouraging, satisfactory.