double-cross

Short definition from Wiktionary

Verb

1. 1
   To betray or go back on; to deceive someone after having gained their trust and led them to believe that they were being aided.
2. 2
   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.
3. 3
   Alternative form of double-cross.

Noun

1. 1
   An instance of betrayal of one who had been led to believe that the betrayer was assisting them.
2. 2
   The hybrid product of double-crossing.
3. 3
   Alternative form of double-cross.