[ in-di-key-ter ]
/ ˈɪn dɪˌkeɪ tər /


a person or thing that indicates.
a pointing or directing device, as a pointer on the dial of an instrument to show pressure, temperature, speed, volume, or the like.
an instrument that indicates the condition of a machine or the like.
an instrument for measuring and recording variations of pressure in the cylinder of an engine.
  1. a substance, as litmus, that indicates the presence or concentration of a certain constituent.
  2. a substance often used in a titration to indicate the point at which the reaction is complete.
Ecology. a plant, animal, or species that indicates, by its presence in a given area, the existence of certain environmental conditions.


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Origin of indicator

1660–70; < Medieval Latin indicātor, equivalent to Latin indicā(re) to indicate + -tor -tor Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Example sentences from the Web for indicator

British Dictionary definitions for indicator

/ (ˈɪndɪˌkeɪtə) /


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

Medical definitions for indicator

[ ĭndĭ-kā′tər ]


One that indicates, especially a pointer or an index.
An instrument used to monitor the operation or condition of an engine, an electrical network, or another physical system; a meter or gauge.
The needle, dial, or other registering device on such an instrument.
Any of various substances, such as litmus or phenolphthalein, that indicate the presence, absence, or concentration of another substance or the degree of reaction between substances by means of a characteristic change, especially in color.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Scientific definitions for indicator

[ ĭndĭ-kā′tər ]

A chemical compound that changes color and structure when exposed to certain conditions and is therefore useful for chemical tests. Litmus, for example, is an indicator that becomes red in the presence of acids and blue in the presence of bases.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.