Definitions
1.nounThe portion of the playing area where one can legally play the ball, puck, etc.
2.nounThe side of a vehicle on which the driver primarily propels it.
3.adjectiveNot in an offside position; In the part of the playing area where one can legally play the ball, puck, etc."The goal was allowed because the attacker was onside."
4.adjectiveOn the side of a vehicle from which the driver, paddler, etc. propels it.
5.adjectiveFavourably located, from the point of view of the player taking a finesse.
6.adjectiveIn agreement or support; on board.