traicionar

traicionar tray-syohn-ahr' (verb)
to betray
1. El espía lo enviaron a la cárcel por haber traicionado su país.

The spy was sent to prison for having betrayed his country.

2. Rompí con mi novio porque me traicionó; besó a mi mejor amigo.

I broke up with my girlfriend because she betrayed me; she kissed my best friend.