Taximeter

n. device in taxicabs to register fare due

A taximeter is a mechanical or electronic device installed in taxicabs, similar to an odometer, which calculates passenger fares based on a combination of distance travelled and waiting time. It is the shortened form of this word that gives the "taxi" its name.
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Noun
1. a meter in a taxi that registers the fare (based on the length of the ride)
(hypernym) meter

n. taximeter

A mechanical or electrical device in a taxicab that records and indicates a charge or fare calculated according to distance traveled, waiting time, initial charge, number of passengers, and other charges authorized by ordinance or by rule. Some taximeters are part of electronic dispatching systems. (TRB1)