To converse or chat (with someone or a group of people) in an easy, friendly manner; to mix or fit in well (with someone or a group of people). I've got to talk to Mike for a while about a work issue, so why don't you go and mingle in with some of the other people at the party, and I'll join you in a minute. I was worried that Tommy wouldn't like starting play school, but it's great to see him mingling in right away.