Synonyms for Untrustworthy (same or very similar meaning)
WordNet sense 1 (not to be trusted):
slippery, trickyWordNet sense 2 (of businesses and businessmen of questionable honesty):
shadyWordNet sense 3 (characterized by insincerity or deceit; evasive):
deviousWordNet sense 4 (not worthy of trust or belief):
untrustyFrom the ODE community, based on WordNetadd/edit