Walk-on

One of a basic set of commands used by Shepherds when commanding sheep-herding dogs, (esp. Border Collies). Walk-on or Walk-up is used in the fetch and in the drive of the flock. Walk-On relays to the dog that the Shepherd wants it to walk straight to the flock and drive them away from the Shepherd or towards the Shepherd depending on the direction the dog is facing. (also see Sheep-herding commands)

In college athletics, a walk-on is a team member who was neither recruited nor awarded a scholarship. Walk-ons are everyday students who got into college the usual way (by demonstrating academic, not athletic, proficiency). They generally earn their spot on the team by performing well in open tryouts--sessions at which any student can show up and demonstrate his or her skills. Most walk-ons spend their
athletic careers as benchwarmers or practice players, but some occasionally play well enough to earn a scholarship or a place in the starting lineup.

A walk-on in a movie or television show is a very small role, similar to a cameo. However, cameos are reserved for the very famous, while any Joe Schmoe can do a walk-on.

Walk-ons are different than extras in that extras don't talk and exist to fill in the background of a scene. A walk-on actor's appearance is usually important to the plot, although usually very short - usually under a minute.

If you get a walk-on role in a horror film, you will probably be killed very quickly and unexpectedly - in the movie, that is, not real life.