a. 不忠贞的, 背信的, 有异心的

[ adj ]
tending to betray; especially having a treacherous character as attributed to the Carthaginians by the Romans
<adj.all>
Punic faiththe perfidious Judas
the fiercest and most treacherous of foes
treacherous intrigues

Perfidious \Per*fid"i*ous\ (p[~e]r*f[i^]d"[i^]*[u^]s; 277), a.
[L. perfidious.]
1. Guilty of perfidy; violating good faith or vows; false to
trust or confidence reposed; teacherous; faithless; as, a
perfidious friend. --Shak.

2. Involving, or characterized by, perfidy. ``Involved in
this perfidious fraud.'' --Milton.