1. a person who is enthusiastic about cars, engines, or mechanical devices and enjoys working on or modifying them
Usage: informal; often used affectionately or neutrally
2. a person who is very interested in or knowledgeable about technical equipment, gadgets, or technology
Usage: informal; extended sense

Examples

• My brother is a real gearhead who spends every weekend working on his truck.
• The gearheads at the car show were discussing engine modifications.
• She's a gearhead when it comes to motorcycles and knows everything about them.
• He became a gearhead after restoring his first classic car.
• The local gearhead community meets monthly to share tips and tricks.
• As a gearhead, he couldn't resist buying that vintage engine.