tro·pism (tr??p?z??m)n. The turning or bending movement of an organism or a part of an organism in a particular direction in response to an external stimulus such as light or gravity.[From -tropism.]tro?pic, tro·pis?tic adj.tro·pis?ti·cal·ly adv.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.tropism (?tr??p?z?m) n (Biology) the response of an organism, esp a plant, to an external stimulus by growth in a direction determined by the stimulus[from Greek tropos a turn] ?tropis?matic adj tropistic adjCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014tro?pism (?tro? p?z ?m) n. the orientation of an organism toward or away from a stimulus, as light. [1895?1900; independent use of -tropism] tro?pis?tic (-?p?s t?k) adj. -tropism var. of -tropy. [see -tropy, -ism] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.tro·pism (tr??p?z??m) Growth or movement of a plant or animal toward or away from an external stimulus, such as light, heat, or gravity.tropistic adjectiveThe American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.tropismthe tendency of a plant, animal, or part to move or turn in response to an external stimulus, as sunlight or temperature. ? tropistic, adj.See also: Motion-Ologies & -Isms. Copyright 2008 The Gale Group, Inc. All rights reserved.tropismDirectional growth movement of a plant in response to a stimulus.Dictionary of Unfamiliar Words by Diagram Group Copyright © 2008 by Diagram Visual Information Limited