Definition of d'Alembert, Jean le Rond in English:
d'Alembert, Jean le Rond
proper nounˈdaləmbɛːdalɑ̃bɛʀ
(1717–83), French mathematician, physicist, and philosopher. His most famous work was the Traité de dynamique (1743), in which he developed his own laws of motion. From 1746 to 1758 he was Diderot's chief collaborator on the Encyclopédie.