(chemistry) The mass of an individual molecule of an element or compound.

Alternative form of Mason-Dixon Line

(physics) The amount of fissile material needed to support a self-sustaining nuclear chain reaction. / (figuratively) The tipping point.

A warm cap shielding the neck and head, often made out of wool and used in skiing, or stereotypically while committing a robbery.

Alternative spelling of facemask

plural of face mask penalty

(American football) A penalty in American football where one player grabs the face mask of an opposing player. There are two versions of this penalty: incidental face mask penalty and the more serious personal foul face mask penalty.

Someone who enjoys pain or humiliation, or who derives pleasure from harming oneself or being harmed by others.

the fruit or mast of the beech tree; beechnuts

(physics, chemistry) a technique of separating ions of different masses by measuring the time taken to traverse a fixed distance through a magnetic field