The Collaborative International Dictionary
Digitorium
Digitorium \Dig`i*to"ri*um\, n. [NL., fr. L. digitus a finger.] A small dumb keyboard used by pianists for exercising the fingers; -- called also dumb piano.
Wiktionary
digitorium
n. A small keyboard used by pianists for exercise the fingers, without producing any sound; a dumb piano.