perfidious
adj.
1590s, from Latin perfidiosus "treacherous," from perfidia (see perfidy). Related: Perfidiously; perfidiousness.
〔李〕[per-=through, to destruction穿透，毁坏；fid=trust信仰；-i-;-ous a.=causing使……的→“cauing one's trust to destruction使信仰彻底破坏的”→] a. faithless;unfaithful;violating faith不忠的；背信的；叛卖的