tricyclic [trahy-sahy-klik, -sik-lik] Word Origin adjective

  1. pertaining to or embodying three cycles.


  1. Also called tricyclic antidepressant. Pharmacology. any of a group of pharmacologically active substances, as imipramine, that share a common three-ring structure, used to treat depression and cocaine abuse.

Origin of tricyclic First recorded in 1890–95; tri- + cyclic Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019 British Dictionary definitions for tricyclic tricyclic adjective

  1. (of a chemical compound) containing three rings in the molecular structure


  1. an antidepressant drug having a tricyclic molecular structure

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 tricyclic in Science tricyclic [trī-sī′klĭk, -sĭk′lĭk]

  1. Relating to a chemical compound having three closed rings. Anthracene is a tricyclic hydrocarbon.
  2. Relating to a class of drugs used to treat depression and having a tricyclic chemical structure consisting of two benzene rings fused to opposite sides of a seven-member ring. The seven-member ring consists of six carbon atoms and one nitrogen atom. Tricyclic antidepressants enhance the activity of monoamine neurotransmitters in the brain by inhibiting their reuptake by the cells that secrete them.
  3. Composed of or arranged in three distinct whorls, as the petals of a flower.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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