| Noun | 1. | M-theory - (particle physics) a theory that involves an eleven-dimensional universe in which the weak and strong forces and gravity are unified and to which all the string theories belong framework, model, theoretical account - a hypothetical description of a complex entity or process; "the computer program was based on a model of the circulatory and respiratory systems" string theory - (particle physics) a theory that postulates that subatomic particles are one-dimensional strings high energy physics, high-energy physics, particle physics - the branch of physics that studies subatomic particles and their interactions |