1 not showing deep understanding or knowledge of any subject -- 膚淺的,理解不深的
She's the author of some fairly lightweight historical novels. 她寫了幾部內容相當膚淺的歷史小說。
2 in some sports, including boxing, a person whose weight is between featherweight and welterweight -- 輕量級運動員
3 a person whose work in a particular area of activity does not show a deep understanding or knowledge of that subject -- 一知半解的人,理解不深的人