A crush was an injury caused by the application of extreme force or pressure to a body part.
In 2368, Worf's spinal cord was crushed and he was left paralyzed. Doctor Beverly Crusher welcomed Captain Jean-Luc Picard to visit Worf in sickbay, but told him not to expect a lot of conversation as Worf was in "full Klingon mode;" honorable, strong, and closed-minded. (TNG: "Ethics")