1. a surgical procedure used to diagnose disease when less invasive methods are inconclusive. 2. a method used by people for feeling the surfaces of objects. People tend to modify their use of touch to optimize the acquisition of information. Thus, they may push on a surface to judge its hardness or stroke it with the index finger to perceive texture. [described in 1987 by Canadian psychologist Susan J. Lederman and U.S. psychologist Roberta L. Klatzky (1947– )]