Out of all the people you could be chilling with they're the one you always with. Number one on your list, they're might be others but that's the one you always roll with.
"I can't go out tonight I'm gonna try and chill with my main squeeze. "
This humorous phrase dates back to the 1800s, when it referred to a powerful or important person. In the 1970s, it began to refer to romantic partners.