"undependable" in the adjective sense
1. unreliable, undependable
not worthy of reliance or trust
"in the early 1950s computers were large and expensive and unreliable"
"an undependable assistant"
2. undependable, unreliable
liable to be erroneous or misleading
"an undependable generalization"
Source: WordNet® (An amazing lexical database of English)
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