Definitions for "PLAY THROUGH"
When a group or player will pass a group of slower golfers playing on the hole ahead. In terms of proper etiquette, it is recommended you ask permission before moving ahead.
When a player(s) invites the player(s) behind them to play ahead of them. If a group is playing slowly it is good etiquette to allow the players behind them to "play through".
(aka: "go through") passing the group in front of you (for various reasons) while they wait. Example: "The group in front of us had two very slow inexperienced players, so they let us play through.