undependable has 1 distinct synonym spread across 2 of its 2 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is dependable.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
not worthy of reliance or trust
“in the early 1950s computers were large and expensive and unreliable”
Synonyms, antonyms and the broader and narrower relations for undependable come from Princeton University’s WordNet. Full sources and licences.