Definition: Barkies are side bets that are won by a golfer who makes par on a hole on which he's hit a tree. Most groups playing Barkies stipulate that leaves don't count - the ball must make contact with wood. A double barkie is worth twice the bet and involves making par despite hitting two trees on the same hole.
Of course, no golfer wants to hit a tree, so Barkies are not things that a golfer sets out to do. But it can add a fun side game to a round of golf and is a good reward for a golfer who recovers for par after hitting a tree.