tax·i·me·ter 
(tăksē-mē′tər)
(tăksē-mē′tər)n.
An instrument installed in a taxicab to measure distance traveled and waiting time and to compute and indicate the fare.
[French taximètre, alteration of taxamètre, from German Taxameter : Medieval Latin taxa, tax (from taxāre, to tax; see TAX) + -meter, meter (from Greek metron, measure; see -METER).]