Found 2 items, similar to mainspring.
English → English (WordNet) Definition: mainspring mainspring n : the most important spring in a mechanical device (especially a clock or watch); as it uncoils it drives the mechanism
English → English (gcide) Definition: mainspring mainspring \main"spring`\, n. The principal or most important spring in a piece of mechanism, especially the moving spring of a watch or clock or the spring in a gunlock which impels the hammer. Hence: (Fig.) The chief or most powerful motive; the efficient cause of action; as, the mainspring of action. [1913 Webster]