1. 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. 2. To enlarge upon; to relate at large; to tell copiously or diffusely. [R.] Do me the favor to dilate at full What hath befallen of them and thee till now. Shak. Syn. -- To expand; swell; distend; enlarge; spread...