perfidious

As adjectives the difference between perfidious and perpetual

is that perfidious is of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance while perpetual is lasting forever, or for an indefinitely long time.

As adjectives the difference between perfidious and meticulous

is that perfidious is of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance while meticulous is (archaic) timid, fearful, overly cautious.

Immoral is a related term of perfidious.

As adjectives the difference between immoral and perfidious

is that immoral is not moral; inconsistent with rectitude, purity, or good morals; contrary to conscience or the divine law while perfidious is of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance.

As adjectives the difference between perfidious and spurious

is that perfidious is of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance while spurious is false, not authentic, not genuine.

Detestable is a related term of perfidious.

As adjectives the difference between detestable and perfidious

is that detestable is detestable, despicable while perfidious is of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance.

Perfidious is a related term of inconstant.

As adjectives the difference between perfidious and inconstant

is that perfidious is of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance while inconstant is not constant; wavering.

Perfidious is a related term of disaffected.

As adjectives the difference between perfidious and disaffected

is that perfidious is of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance while disaffected is alienated or estranged, often with hostile effect; rebellious, resentful; disloyal.

As a verb disaffected is

(disaffect).

As a noun treachery

is deliberate, often calculated, disregard for trust or faith.

As an adjective perfidious is

of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance.

As adjectives the difference between treasonous and perfidious

is that treasonous is like or in the way of treason while perfidious is of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance.

As adjectives the difference between incontinent and perfidious

is that incontinent is unable to contain or retain while perfidious is of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance.

As a noun incontinent

is one who is unchaste.