Definitions

1. adverb

on the side of a field or playing area, especially in American football, that a team is attacking from, or on the side of the field that a player is considered to be on when a penalty is committed.

“The quarterback threw the touchdown pass from the onside kick.”

2. adjective

being on the same side of a boundary or line as something else.

“The onside houses are facing the park.”

3. noun

a kick that is made from the side of the field or playing area, in an attempt to gain possession of the ball.

“The onside kick was a crucial play in the game.”