Headspace

Origin

head + space

Full definition of headspace

Noun

1. The space between the top of the contents of a container (such as a jar) and its seal (such as a lid).
2. (informal) One's mental state.
• 1996, Andrew Cowan, Common GroundIt's like, I need to clear my headspace but I can't do that with him around because he's just ego, you know? He dumps on me. So that's it.
3. (firearms) The gap between the face of the bolt and the stopping surface for the cartridge.