underlever

plural underlevers

1. A lever behind the trigger guard of a rifle

   Incidentally, the current underlevers developed and produced after World War II are vastly improved over the prewar types, though millions of the latter are still used.

   1957, Walter Harold Black Smith, Gas, Air, and Spring Guns of the World, page 113

2. A particular piano component.

   The wippen, a mechanism of underlevers, controls the jacks that push the hammers up to the strings.

   1996, Susan Goldenberg, Steinway from Glory to Controversy: The Family, the Business, the Piano

   1 more example

   The second assembly is the underlever / damper assembly which comprises all the linkage that activates the damper system, which stops the tone when the key is pressed.

   2008, Marty C. Flinn, The Complete Idiot's Guide to Buying a Piano, page 113