game of chance; luck-based game
Slang abbreviation of 運ゲーム. Used in gaming contexts to describe a game or situation where luck, rather than skill, determines the outcome.
This boss has random attack patterns; it's totally a game of chance.
Abbreviation of 運ゲーム (un-gēmu), from 運 (un, 'luck') + ゲーム (gēmu, 'game').