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Someone who repairs cars informally or as a hobby. Grandpa seems to love being retired. He's always been a bit of a shadetree mechanic, but now it's become his passion. You've got a pretty big problem with your transmission right now, more than this shadetree mechanic can diagnose. You'll have to take it to a professional.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.