Why was "tantrum" trending last week?


[troh-piz-uh m] /ˈtroʊ pɪz əm/
noun, Biology
an orientation of an organism to an external stimulus, as light, especially by growth rather than by movement.
1895-1900; independent use of -tropism
Related forms
[troh-piz-mat-ik] /ˌtroʊ pɪzˈmæt ɪk/ (Show IPA),
[troh-pis-tik] /troʊˈpɪs tɪk/ (Show IPA),
adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
Cite This Source
British Dictionary definitions for tropistic


the response of an organism, esp a plant, to an external stimulus by growth in a direction determined by the stimulus
Derived Forms
tropismatic, adjective
tropistic (trəʊˈpɪstɪk) adjective
Word Origin
from Greek tropos a turn
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
Word Origin and History for tropistic



1899, "tendency of an animal or plant to turn or move in response to a stimulus," abstracted from geotropism, ultimately from Greek tropos (see trope).

Online Etymology Dictionary, © 2010 Douglas Harper
Cite This Source
tropistic in Medicine

tropism tro·pism (trō'pĭz'əm)
The turning or bending movement of a living organism or part toward or away from an external stimulus, such as light, heat, or gravity.

tro'pic, tro·pis'tic adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Cite This Source
tropistic in Science
The growth or movement of a living organism or anatomical structure toward or away from an external stimulus, such as light, heat, or gravity. See also geotropism, hydrotropism, phototropism.

tropistic adjective
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
Cite This Source
Encyclopedia Article for tropistic


response or orientation of a plant or certain lower animals to a stimulus that acts with greater intensity from one direction than another. It may be achieved by active movement or by structural alteration. Forms of tropism include phototropism (response to light), geotropism (response to gravity), chemotropism (response to particular substances), hydrotropism (response to water), thigmotropism (response to mechanical stimulation), traumatotropism (response to wound lesion), and galvanotropism, or electrotropism (response to electric current). Most tropic movements are orthotropic; i.e., they are directed toward the source of the stimulus. Plagiotropic movements are oblique to the direction of stimulus. Diatropic movements are at right angles to the direction of stimulus.

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

Word of the Day

Difficulty index for tropism

Few English speakers likely know this word

Word Value for tropistic

Scrabble Words With Friends

Nearby words for tropistic