The Collaborative International Dictionary of English v.0.48:
Plessimeter \Ples*sim"e*ter\, n. See Pleximeter. [1913 Webster]WordNet (r) 3.0 (2006):
plessimeter n 1: a small thin metal plate held against the body and struck with a plexor in percussive examinations [syn: pleximeter, plessimeter]