Temperature of the free air as measured with a dry thermometer on a sling psychrometer over a grassy surface at a height of approximately 6 feet (1.8 meters)
A hygrometer consisting of two thermometers, the bulb of one of which is kept wet and shows a lower temperature; the relative humidity is obtained from the two temperatures using tables
[ 'drI ] (adjective.) before 12th century. Middle English, from Old English dryge; akin to Old High German truckan dry, Old English drEahnian to drain.