or phase-out



an act or instance of phasing out; planned discontinuation or expiration.

Nearby words

  1. phase-contrast microscope,
  2. phase-in,
  3. phase-switching,
  4. phased array,
  5. phasedown,
  6. phases of matter,
  7. phasing,
  8. phasis,
  9. phasmid,
  10. phasor

Origin of phaseout

First recorded in 1955–60; noun use of verb phrase phase out




any of the major appearances or aspects in which a thing of varying modes or conditions manifests itself to the eye or mind.
a stage in a process of change or development: Each phase of life brings its own joys.
a side, aspect, or point of view: This is only one phase of the question.
a state of synchronous operation: to put two mechanisms in phase.
  1. the particular appearance presented by the moon or a planet at a given time.
  2. one of the recurring appearances or states of the moon or a planet in respect to the form, or the absence, of its illuminated disk: the phases of the moon.
Zoology. color phase.
Chemistry. a mechanically separate, homogeneous part of a heterogeneous system: the solid, liquid, and gaseous phases of a system.
Physics. a particular stage or point of advancement in a cycle; the fractional part of the period through which the time has advanced, measured from some arbitrary origin often expressed as an angle (phase angle), the entire period being taken as 360°.

verb (used with object), phased, phas·ing.

to schedule or order so as to be available when or as needed.
to put in phase; synchronize: to phase one mechanism with another.

Verb Phrases

phase down, to reduce by gradual stages.
phase in, to put or come into use gradually; incorporate by degrees: to phase in new machinery.
phase out, to bring or come to an end gradually; ease out of service: to phase out obsolescent machinery.

Origin of phase

1805–15; (noun) back formation from phases, plural of phasis

Related forms
Can be confusedfaze phase Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for phase out

phase out


(tr, adverb) to discontinue or withdraw gradually

noun phase-out

the action or an instance of phasing outa phase-out of conventional forces



any distinct or characteristic period or stage in a sequence of events or chain of developmentthere were two phases to the resolution; his immaturity was a passing phase
astronomy one of the recurring shapes of the portion of the moon or an inferior planet illuminated by the sunthe new moon, first quarter, full moon, and last quarter are the four principal phases of the moon
  1. the fraction of a cycle of a periodic quantity that has been completed at a specific reference time, expressed as an angle
  2. (as modifier)a phase shift
physics a particular stage in a periodic process or phenomenon
in phase (of two waveforms) reaching corresponding phases at the same time
out of phase (of two waveforms) not in phase
chem a distinct state of matter characterized by homogeneous composition and properties and the possession of a clearly defined boundary
zoology a variation in the normal form of an animal, esp a colour variation, brought about by seasonal or geographical change
biology (usually in combination) a stage in mitosis or meiosisprophase; metaphase
electrical engineering one of the circuits in a system in which there are two or more alternating voltages displaced by equal amounts in phase (sense 5)See also polyphase (def. 1)
(in systemic grammar) the type of correspondence that exists between the predicators in a clause that has two or more predicators; for example connection by to, as in I managed to do it, or -ing, as in we heard him singing

verb (tr)

(often passive) to execute, arrange, or introduce gradually or in stagesa phased withdrawal
(sometimes foll by with) to cause (a part, process, etc) to function or coincide with (another part, process, etc)he tried to phase the intake and output of the machine; he phased the intake with the output
mainly US to arrange (processes, goods, etc) to be supplied or executed when required
Derived Formsphaseless, adjectivephasic or phaseal, adjective

Word Origin for phase

C19: from New Latin phases, pl of phasis, from Greek: aspect; related to Greek phainein to show

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

Word Origin and History for phase out
Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for phase out




A characteristic form, appearance, or stage of development that occurs in a cycle or that distinguishes some individuals of a group.
A discrete homogeneous part of a material system that is mechanically separable from the rest, as is ice from water.
Any of the forms or states, solid, liquid, gas, or plasma, in which matter can exist, depending on temperature and pressure.
A particular stage in a periodic process or phenomenon such as a wave form or time pattern.


To introduce, one stage at a time.

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

Science definitions for phase out



Any of the forms, recurring in cycles, in which the Moon or a planet appears in the sky.
One of a set of possible homogenous, discrete states of a physical system. States of matter such as solid and liquid are examples of phases, as are different crystal lattice structures in metals such as iron. See also phase transition state of matter.
A measure of how far some cyclic behavior, such as wave motion, has proceeded through its cycle, measured in degrees or radians. At the beginning of the phase, its value is zero; at one quarter of its cycle, its phase is 90 degrees (π/2 radians); halfway through the cycle its value is 180 degrees (π radians), and so on.♦ The phase angle between two waves is a measure of their difference in phase. Two waves of the same frequency that are perfectly in phase have phase angle zero; if one wave is ahead of the other by a quarter cycle, its phase angle 90 degrees (π/2 radians); waves that are perfectly out of phase have phase angle 180 degrees (π radians), and so on. See more at wave.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.