You bump into someone you don't like, they clearly want a stop and chat but quick as a flash you say "must go" and start to leave, but they come along too still babbling shit. You're pissed off, you want to hit them, you're in a walk and talk. (Not as cool as it looks on the west wing).
Jim: Saw that tosser Mike today, tried to get me in a stop and chat but i said i had to rush to meet someone.
The process in which two or more people notice that one of their friends is walking/flirting with a person that is way too attractive for them. Thus, to break up the social engagement the initial group that noticed the flirting catches up to the canoodling couple and initiates a conversation to prevent the pair from flirting further.
Guy A: Dude, did you see Carl and Vanessa walking to class together.