1 [countable/uncountable] the part of an engine that changes engine power into movement. Most cars in the UK have 5 or 6 gears that you operate yourself
first/second etc gear:
At forty miles an hour you should be in fourth gear.
grind/crash the gears (=make a noise when changing gear because you do not do it correctly):
You’ll ruin the gearbox if you keep grinding the gears like that.
in gear (=with one of the gears connected so that the power of the engine will make the wheels move):
The car won’t move unless you’re in gear.
out of gear (=with no gears connected):
Take the car out of gear.
Synonyms and related words