To get in on is defined as becoming involved in something or becoming a part of the action.
An example of get in on is when a person puts his $5 bet in with the money all of his other friends have pooled in order to do something together.
Browse entries near get in on
gesundheit
get go
get carried away
get-go
get hip to
get in someones face
get on it
get-out
get the drop on
get the hang of