Seats in the nosebleed section of an arena or other sports stadium.

A term used to reference cannabis/marijuana/weed.

Sometimes used in anime and manga, nosebleed means to become sexually excited. It's usually embarrassing and something the character will probably try to cover up. Though it normally is shown happening to male characters, female characters have also been shown having nosebleeds.
It is also a term used by fans, regardless of their type of fandom, to express finding something exciting sexually or hot.

A less embarassing but more irritating alternative to developing a boner.

a Filipino street slang that means running out of English words to say , or is in a state of difficulty understanding particularly English language. may sometimes be applicable aside from English like math problems.

Something that happens to anime characters (particularly males), outside of hentai, when they are confronted with a sexually exciting situation.

Nose bleed seats are seats far away and high up on the stands. It comes from the real nose bleeding which occurs at actual high altitudes.