Why was "tantrum" trending last week?


[hee-lee-uh-stat] /ˈhi li əˌstæt/
an instrument consisting of a mirror moved by clockwork, for reflecting the sun's rays in a fixed direction.
1740-50; < New Latin heliostata. See helio-, -stat
Related forms
heliostatic, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
Cite This Source
British Dictionary definitions for helio-static


an astronomical instrument used to reflect the light of the sun in a constant direction
Derived Forms
heliostatic, adjective
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Cite This Source
Encyclopedia Article for helio-static


instrument used in solar telescopes to orient and focus sunlight along a fixed direction. A typical heliostat consists of a flat plane mirror and a curved parabolic mirror. The plane mirror is mounted along an axis parallel (i.e., equatorial) to the Earth and rotated slowly by a motor to reflect light from the Sun. The parabolic mirror focuses the reflected rays into the telescope along a fixed direction while the Sun traverses the sky. Therefore, as the telescope's field of view rotates, different celestial objects move quickly into view

Learn more about heliostat with a free trial on
Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
Cite This Source

Word of the Day

Difficulty index for heliostat

Few English speakers likely know this word

Word Value for helio

Scrabble Words With Friends

Quotes with helio-static