plain /plein/ I. n. ［c］ 平原,平地, 旷野：The great plains of American Midwest is very beautiful.美国中西部的大平原是非常美的。‖II. adj. 清楚的, 平凡的: Let us be plain with you.让我们坦白地对你说。From a rather plain child she had grown into a beautiful woman. 她从一个相貌平常的孩子长成一个美丽的女子。‖III. adv.平易地，明白地，完全地，显然地：write plain写清楚 That is just plain stupid.那简直是愚蠢透顶。