antiparticle: a particle that has the same mass as another particle but has opposite values for its other properties; interaction of a particle and its antiparticle results in annihilation and the production of radiant energy
elementary particle: (physics) a particle that is less complex than an atom; regarded as constituents of all matter
liquid diet: a diet of foods that can be served in liquid or strained form (plus custards or puddings); prescribed after certain kinds of surgery