grand unified theory

from The Collaborative International Dictionary of English v.0.48

grand unified theory \grand unified theory\, grand unification
theory \grand unification theory\n. (Theoretical physics)
   Any of a class of physics theories that attempts to explain
   the electroweak forces, stong force, and gravitation within a
   single mathematical conceptual scheme. In the 1990's {string
   theory} and {superstring theory} were prominent examples.
   Abbreviated GUT, plural GUTs.
   [PJC]