double-cross

verb

to betray by contradicting prior agreement

Wiktionary

noun

Etymology: First recorded in 1834 from thieves' slang cross (or on the cross) to refer to something dishonest, a play on straight or square: a crook going back on his partners would therefore be crossing the crossers, or double-crossing.

An act or instance of deliberate betrayal or deceit, especially in which one party violates a prior agreement or trust with a collaborator.
“The only problem is that Cosmo accidentally double-crosses the double-cross: By sheer luck he succeeds at the murder and gets away, which leaves the mob in the uncomfortable position of having to do the dirty work of rubbing him out themselves.”
Of a breeding, the hybrid product of double-crossing.

verb

To betray or go back on; to deceive someone after having gained their trust and led them to believe that they were being aided.
“If you double-cross us, we'll track you down and kill you.”
“I've been double crossed / By a double dealin', double winnin' / Looks like I'm the one who lost.”
Of breeding, to cross twice in hybridization, as (A × B) × (C × D); for example, in commercial hybrid seed corn, A through D are classically inbreds, and their grandoffspring is the seed for sale.