headroom

1. The vertical clearance above someone's head, as in a tunnel, doorway etc; room (space) for one's head. (countable, uncountable)
2. The vertical measurement, top to bottom, for example for clearance under a bridge. (countable, uncountable)
3. The ability of a system to reproduce loud sounds free of distortion; dynamic headroom. (countable, uncountable)
4. The distance between the actual performance of an algorithm and its maximum possible performance. (countable, uncountable)
5. Synonym of headspace (“space between the top of the contents of a container and its seal”). (countable, uncountable)

Plural headrooms