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1. adjective Trivial; unimportant; inconsequential. It's an admirable attempt by the director to branch out into more serious subject matter, but, ultimately, maybe he would be better off sticking to the lightweight comedies he's known for. We only have a short amount of time for this meeting, so let's stick with the lightweight issues. We can tackle the bigger problems when I'm back from New York next week. I'm not going to let some lightweight graduate come in and undo all the work I've done on this case.
2. noun An unskilled, unimpressive, or unimportant person. They thought she was just a lightweight because she was inexperienced and kept to herself, but she ended up getting the best sales of the entire team last year. Kid, I've been doing this job for nearly 30 years—I don't need a lightweight like you giving me advice.
3. noun Someone who becomes affected by alcohol very quickly and severely. Jane is a total lightweight—two beers and she's totally out of it. I used to be able to party until the early hours when I was in college, but I've become a lightweight since having kids.
1. mod. inconsequential. This is a fairly lightweight matter.
2. n. an inconsequential person; someone who accomplishes very little. Don’t worry about her. She’s just a lightweight.