The Collaborative International Dictionary
suck face
suck face \suck face\, v. i. To engage in french kissing (soul-kissing). [slang]
Wiktionary
suck face
vb. (context idiomatic colloquial English) To kiss, especially deeply and for a prolonged time.
Usage examples of "suck face".
Third Eye Blind and bicycle shorts topped the list, but watching Claire suck face with a hunka, hunka burning love in the front yard followed close behind.