to expand; to distend; to enlarge or extend in all directions; to swell; -- opposed to contract; as, the air dilates the lungs; air is dilated by increase of heat.-to enlarge upon; to relate at large; to tell copiously or diffusely.-to grow wide; to expand; to swell or extend in all directions.-to speak largely and copiously; to dwell in narration; to enlarge; -- with on or upon.-extensive; expanded.