- dee⇄adj. shaped like a D.
- dee⇄dee, noun, adjective.
- dee⇄noun 1. the letter D or d.
2. either of the two D-shaped, semicircular, hollow cylinders of a cyclotron. When electrons are accelerated in the dees to a speed of 28,000 miles per second they are released to create a beam in the cyclotron.