get in on something

Từ điển Oxford Advanced Learner 8th

▪ I. ˌget ˈin on sth derived
to take part in an activity
•He's hoping to get in on any discussions about the new project.
Main entry: ↑get_derived
 
▪ II. be/get ˈin on sth idiom
(informal)to be/become involved in sth; to share or know about sth
•I'd like to be in on the plan.
•Is she in on the secret?
Main entry: ↑in_idiom