From Wiktionary, the free dictionary
walk on (third-person singular simple present walks on, present participle walking on, simple past and past participle walked on)
- (theater) To come onstage.
He walks on after your line.
- (idiomatic) To join a college sports team without being recruited for it.
He walked on this year.
- Used other than figuratively or idiomatically: see walk, on.
