Mangalawang (en. Second)

/maŋɡaˈlawang/

Slang Meanings

It means having another romantic relationship while currently being in one.
Dude, it looks like you're going to cheat on your new girlfriend again.
Pare, mukhang mangangalawang ka na naman sa bago mong jowa.
Being unfaithful or not loyal to your partner.
I never thought he would cheat; I thought he was loyal.
Hindi ko akalaing mangangalawang siya; akala ko loyal siya.