Antonyms for the word "play game" could include words like work, labor, seriousness, drudgery, and solemnity. When we think of opposing terms for "play game," the antonyms tend to evoke notions of productivity, responsibility, and gravity. For example, while playing a game is typically seen as a leisurely activity that one engages in for fun or relaxation, work is often seen as a more serious endeavor that requires focused attention and effort. Labor, too, suggests a sense of toil and hard work, while solemnity implies a weighty and serious mood. Therefore, antonyms for "play game" are generally terms that connote a seriousness of purpose, focus, and intention.