A narrow, slender saw, used in cutting keyholes, etc.

plural of keyhole saw

plural of keyhole limpet

plural of keyhole surgery

plural of keyhole urchin

plural of gravitational keyhole

(astronomy) A tiny region of space where a planet's gravity would alter the orbit of a passing asteroid such that the asteroid would collide with that planet on a given future orbital pass.

plural of keyhole wound

A ragged wound caused by a bullet that enters the body at a shallow angle.

(biology) A carrier for making antigens. Because of its large size and distant relation to humans and many test animals, KLH causes a large antigenic response. When paired with a hapten, the hapten also becomes immunogenic.