be a mug's game

be a mug's game

To be a task or activity that is foolish, dangerous, or will not result in a positive outcome. Primarily heard in UK. Allowing your children to play with fireworks is a mug's game. They are bound to get injured.
See also: game

be a ˈmug’s game

(disapproving, especially British English) an activity which brings little or no benefit to you: Don’t start smoking — it’s a mug’s game.The money’s terrible in this job — it’s a real mug’s game.
Mug here means ‘fool’.
See also: game