WordNet sense 1 (having the character of, or characteristic of, a traitor):

faithless, traitorous, treasonable, treasonous

WordNet sense 2 (deserting your allegiance or duty to leader or cause or principle):

disloyal

WordNet sense 3 (not faithful to a spouse or lover):

cheating

WordNet sense 4 (not true to an obligation or trust):

untrue

WordNet sense 5 (tending to betray; especially having a treacherous character as attributed to the Carthaginians by the Romans):

perfidious, treacherous

WordNet sense 6 (not accurate):

inaccurate