sit in with

English

Verb

sit in with (third-person singular simple present sits in with, present participle sitting in with, simple past and past participle sat in with)

  1. (idiomatic) To join (often as an observer, supervisor or outsider) a group working together on a task.
    I'll have to sit in with the interviews for the deputy manager position.
    She sat in with one of his group counseling session.