Definition of gearhead noun from the Oxford Advanced Learner's Dictionary

 

gearhead

 noun
noun
BrE BrE//ˈɡɪəhed//
 
; NAmE NAmE//ˈɡɪrhed//
 
(informal)
 
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a person who is very enthusiastic about cars or new technical devices and equipment He's a total gearhead—can't keep away from the race track. Like most keen cyclists I’m a bit of a gearhead.
See the Oxford Advanced American Dictionary entry: gearhead