- any of several bands of high-velocity winds moving from west to east around the earth at altitudes from c. 12 to 16 km (c. 8 to 10 mi)
- the stream of exhaust from any reaction enginealso written jet′stream·
- A high-speed, meandering wind current, generally moving from a westerly direction at speeds often exceeding 400 kilometers (250 miles) per hour at altitudes of 10 to 15 kilometers (6 to 9 miles).
- A high-speed stream; a jet.
A narrow current of strong wind circling the Earth from west to east at altitudes of about 11 to 13 km (7 to 8 mi) above sea level. There are usually four distinct jet streams, two each in the Northern and Southern hemispheres. Jet stream wind speeds average 56 km (34 mi) per hour in the summer and 120 km (74 mi) in the winter. They are caused by significant differences in the temperatures of adjacent air masses. These differences occur where cold, polar air meets warmer, equatorial air, especially in the latitudes of the westerlies.
(plural jet streams)
- (meteorology) any of the high-speed, high-altitude air currents that circle the Earth in a westerly direction