(US, politics, historical) A 1980s plan whereby all Soviet and American nuclear weapons would be mutually withdrawn from Europe.

zero gravity

The point, during childbirth, at which the baby's head is level with the ischial spines in the maternal pelvis.

(grammar) The absence of an ending after a noun‐stem in a language in which endings are normally applied; often written as ∅

(education) A high school class that is offered early in the morning, before the scheduled start of the school day.

(mathematics) A type of potential counterexample to the generalized Riemann hypothesis, on the zeros of Dirichlet L-function.

(mathematics) A matrix whose entries are all zero.

plural of zero hour

Alternative spelling of zero-grade

(category theory) An object which is both an initial object and a terminal object.