Try Our Apps


Supposedly vs. Supposably


[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.
Origin of tropism
1895-1900; independent use of -tropism
Related forms
[troh-piz-mat-ik] /ˌtroʊ pɪzˈmæt ɪk/ (Show IPA),
[troh-pis-tik] /troʊˈpɪs tɪk/ (Show IPA),


variant of -tropy.
see -tropy, -ism Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
Cite This Source
Examples from the Web for tropism
Contemporary Examples
Historical Examples
  • The workers, on the other hand, who have to be in and out of the nest about their business, do not have this tropism.

    Natural Wonders Edwin Tenney Brewster
  • The object of the tropism is to keep the males and females in the nest until swarming time, and then to get them out.

    Natural Wonders Edwin Tenney Brewster
  • We shall in the succeeding series of papers deal with the subject of tropism in general.

  • Driesch has found that a tropism underlies the arrangement of the skeleton in the pluteus larvae of the sea-urchin.

    Darwin and Modern Science A.C. Seward and Others
  • As a type of human behavior it may be explained, like the attraction of the flame for the moth, as a sort of tropism.

  • This may be a tropism (stereotropism) or it may be a mere surface tension phenomenon.

British Dictionary definitions for tropism


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


combining form
indicating a tendency to turn or develop in response to a certain stimulus: phototropism
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 tropism

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
tropism 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.

-tropism suff.
Tropism: stereotropism.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Cite This Source
tropism 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

Word of the Day

Difficulty index for tropism

Few English speakers likely know this word

Word Value for tropism

Scrabble Words With Friends

Nearby words for tropism