(astrophysics) A particle that falls behind the event horizon, for example into a black hole.

(organic chemistry) Any of a class of brown polymers typically formed when food is browned (by means of the Maillard reaction).

Used to express frustration or irritated disbelief, from the tendency of annoyed or irritated people to want to repeatedly bang their heads against their desk.

(US) Initialism of National Roofing Contractors Association.