(idiomatic, colloquial) The important point to consider.

(mathematics) A branch of mathematics which deals with spaces and maps between them in abstraction, taking similar theorems from various disparate more concrete branches of mathematics and unifying them.

(physics) A candidate unified theory of all physical forces and particles; a theory which suggests that subatomic particles are one-dimensional strings rather than zero-dimensional points. It also suggests that space-time can have up to nine dimensions, plus the dimension of time.

The branch of mathematics dealing with the algebraic structure of rings.

Alternative form of where the sun don't shine

(idiomatic) The specific provisions of, or particular steps for implementing, a general plan, policy, or contract may be complicated, controversial, or unworkable.

Often used other than figuratively or idiomatically: to assume a given position.

simple past tense and past participle of buy the farm

(idiomatic) to do something exactly, precisely, or in a formulaic way.

(sports) To feel the burning sensation arising in a muscle being intensely exercised; often used as an exhortation to extend oneself in physical exercise.