The Collaborative International Dictionary of English v.0.48:

Tachograph \Tach"o*graph\, n. [Gr. ta`chos speed + -graph.]
   A recording or registering tachometer; also, its autographic
   record.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

tachograph
    n 1: a tachometer that produces a graphical record of its
         readings; used to record the speed and duration of trips in
         a motor vehicle