faith ‧ less /ˈfeɪθləs/ BrE AmE adjective formal
[ Word Family: noun : ↑ faith , ↑ faithfulness ≠ ↑ unfaithfulness , ↑ faithful , ↑ faithlessness ; adjective : ↑ faithful ≠ ↑ unfaithful , ↑ faithless ; adverb : ↑ faithfully ≠ ↑ unfaithfully ]
someone who is faithless cannot be trusted SYN untrustworthy :
a faithless friend
—faithlessness noun [uncountable]