headroom

Từ điển Oxford Advanced Learner 8th

head·room [headroom] BrE [ˈhedruːm] NAmE [ˈhedruːm] BrE [ˈhedrʊm] NAmE [ˈhedrʊm] noun uncountable
1. the amount of space between the top of a vehicle and an object it drives under
2. the amount of space between the top of your head and the roof of a vehicle
•There's a lot of headroom for such a small car.

Example Bank:
•The new model gives generous headroom for front and rear passengers.
•The sign on the bridge said ‘Maximum Headroom 2.5 metres.’