hy·dro·dy·nam·ics 
(hī′drō-dī-nămĭks)
(hī′drō-dī-nămĭks)n.
1. (used with a sing. verb) The branch of science that deals with the dynamics of fluids, especially incompressible fluids, in motion.
2. (used with a pl. verb) The dynamics of fluids in motion.
hy′dro·dy·nami·cist (-ĭ-sĭst) n.