Other forms: nosebleeds
A nosebleed is a flow of blood from the nostrils. Dramatic, alarming, and usually harmless.
The blood vessels just inside the nose are very close to the surface, which is why dry air, a knock or simply blowing hard sets one off. The advice has changed, and the current guidance is to lean forward and pinch the soft part rather than tipping the head back. There is a figurative use about height, since nosebleed seats are the ones right at the top.
1nounnosebleedAn escape of blood from the nose.
“He got a nosebleed in the second half and had to come off.”
From nose + bleed.
Etymology from Wiktionary, CC BY-SA