To insert something (or oneself) between other things.
To interrupt a conversation by introducing a different subject or making a comment.
To intervene in a dispute, or in a conversation.
To be inserted between parts or things; to come between.
To offer (one's help or services).
To include (e.g. a certain word or phrase) into a sentence discreetly
To enter discreetly
To play a subtle pass into someone in a goalscoring position.