noun
speed per hour; hourly speed
Used to express speed in units per hour, e.g., kilometers per hour (km/h). Often followed by a number and unit.
この車の最高時速は200キロです。
The top speed of this car is 200 kilometers per hour.
時速60キロで走ってください。
Please drive at 60 kilometers per hour.
Compound of 時 (hour) and 速 (speed). The reading じそく is the on'yomi for both characters.