Being not offside in sportsball, i.e., being where one needs to be (being in the right place at the right time).
Since the early 1870s, onside is a compound word signifying, per the rules and regulations of various iterations of team sportsball, that a player is occupying a position on the field (or playing surface) where receiving, playing, or even touching the ball (or puck) is an allowed maneuver because the player is inside the prescribed line or area at the beginning of or during play. Onside can be used to reference the location of the ball or intended maneuver (e.g., an onside kick) as well.
The upside to being onside is that one will not be penalized for being offside, which can be considered a form of cheating.
SQ '24