an iso (short for isolation) is a 1 on 1 situation at a party between a girl and guy in which one person in the conversation is trying to rizz the other. The topic of an iso typically emerges when a guy and a girl are initially in a larger group, but either the guy or girl wants to make a move on the person of the opposite gender. A person can "request" an iso from the other members of the larger group (in which the other members would leave the couple alone), or the members of the larger group can "give" the couple an iso and leave them alone to let the couple cook.
Ex 1: "Hey Katie, can you give me the iso with Jill? I need to rizz this chick and take her home with me."
"Of course, Brad. I will leave immediately"
Ex 2: "Hey Spencer, I see you spitting mad game to Madeline Woods. I'll give you this iso."
*Spencer fist bumps Parker and Parker walks away*