in on, be

be in on (something)

To be participating or involved in something, often something secret or exclusive. The conspiracy ran deep, and several members of the administration were in on it. Wow, that really was a surprise. Were you in on planning this?
See also: on
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

in on, be

Also, get in on. Be or become a participant; be or become one of a group who have information. For example, Is she in on our secret? or I'd like to get in on this venture. [c. 1920] Also see barge in on; ground floor (get in on the); in good with.
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
See also: