Someone who royally F's up everything they do.
That guy who keeps giving away the answer unintentionally is such a dumbler.
by IggyGaara April 12, 2010
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A really bad or dumb bumbler. Basically, one who makes too many mistakes too often without realizing it until later.
The guy who just moved in with me was definitely a dumbler at first but at least it seems he's getting used to things now. So he's good.
by Pseudonymous Johnson June 19, 2020
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