duffer

A duffer is someone who's not very good at sports or games.

When people say "he's such a duffer" they usually mean it as a friendly tease - like when a friend plays poorly in a game and everyone makes fun of them, but still encourages them to keep trying. You might hear this kind of talk at the office when coworkers join in on a casual round of golf or bowling together. Or maybe you've seen it at school, where friends team up for a pick-up basketball game. It's all about having fun and not taking things too seriously - even if someone's getting beaten badly! The phrase is often used to describe people who are beginners or just don't have the knack for a particular activity.