Synonyms for Undependable (same or very similar meaning)
WordNet sense 1 (liable to be erroneous or misleading):
unreliableWordNet sense 2 (likely to fail or make errors):
fallibleWordNet sense 3 (not consistent or dependable):
uncertainWordNet sense 4 (likely to perform unpredictably):
erraticFrom the ODE community, based on WordNetadd/edit