v. 1. To go too slowly: be late; do something too slowly. The post office got behind in delivering Christmas mail.
Synonym: FALL BEHIND.
Antonym: KEEP UP. 2. informal To support; help. A club is much better if members get behind their leaders. We got behind Mary to be class president.
Compare: BACK OF 3 . 3. informal To explain; find out the reason for. The police are questioning many people to try and get behind the bank robbery.
Synonym: GET TO THE BOTTOM OF.