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)
- (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.