from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An instrument that indicates changes in atmospheric humidity.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. An instrument that indicates changes in atmospheric humidity
from the GNU version of the Collaborative International Dictionary of English
- n. An instrument which shows whether there is more or less moisture in the atmosphere, without indicating its amount.
from The Century Dictionary and Cyclopedia
- n. An instrument or apparatus in which the hygroscopic property of some substance is employed for indicating approximately the humidity of the air, without attempting its accurate measurement.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. hygrometer that shows variations in the relative humidity of the atmosphere
hygro- + -scope (Wiktionary)
In this way a small area of the surface of the earth is converted into a hygroscope, and these test surfaces tell us whether the ground is cooled to the dew-point or not.