Synonyms of unstable

unstable

adjective

ˌən-ˈstā-bəl 

1

as in unsteady

not being in or able to maintain a state of balance

the minute we put the books down on the unstable desk, the whole stack went crashing to the floor

Synonyms & Similar Words

• unsteady
• precarious
• rocky
• unbalanced
• uneven
• shaky
• wobbly
• insecure
• wonky
• tipsy
• infirm
• tippy
• rickety
• unsound
• tottering
• lopsided
• doddering
• teetering
• wavery
• awry
• tottery
• doddery
• jiggly
• askew
• jiggling
• staggery
• off-kilter
• cockeyed

Antonyms & Near Antonyms

• stable
• steady
• stabilized
• balanced
• level
• substantial
• straight
• equilibrated
• even
• sound
• sturdy

2

as in volatile

likely to change frequently, suddenly, or unexpectedly

financial investors don't like an unstable economy

Synonyms & Similar Words

• volatile
• unpredictable
• inconsistent
• changeful
• uncertain
• variable
• unsettled
• mercurial
• mutable
• fluctuating
• capricious
• inconstant
• changeable
• temperamental
• unsteady
• fickle
• erratic
• unreliable
• shaky
• fluid
• up in the air
• skittish
• random
• haphazard
• scattered
• flickery
• arbitrary
• aimless
• ambivalent
• untrustworthy
• slapdash
• undependable
• stray
• irregular
• dicey
• hit-or-miss
• desultory
• versatile
• adaptable
• vacillating
• mobile
• protean
• wavering
• hesitating
• shilly-shallying
• shilly-shally

Antonyms & Near Antonyms

• stable
• constant
• certain
• steady
• predictable
• stationary
• unchanging
• invariable
• unchangeable
• immutable
• settled
• uniform
• permanent
• even
• persistent
• changeless
• durable
• unvarying
• lasting
• reliable
• equable
• abiding
• dependable
• true
• sure
• trustworthy
• trusty
• tried
• tried-and-true

3

as in changing

not staying constant

unstable temperatures are not ideal storage conditions for wine

Synonyms & Similar Words

• changing
• uneven
• varying
• volatile
• unequal
• erratic
• changeful
• inconsistent
• unsteady
• fluctuating
• irregular
• uncertain
• variable
• mercurial
• capricious
• unsettled
• changeable
• fickle
• mutable
• inconstant
• fluid
• choppy

Antonyms & Near Antonyms

• stable
• constant
• steady
• unchanging
• regular
• changeless
• unvarying

Synonym Chooser

How does the adjective unstable differ from other similar words?

Some common synonyms of unstable are capricious, fickle, inconstant, and mercurial. While all these words mean "lacking firmness or steadiness (as in purpose or devotion)," unstable implies an incapacity for remaining in a fixed position or steady course and applies especially to a lack of emotional balance.

too unstable to hold a job

When can capricious be used instead of unstable?

The synonyms capricious and unstable are sometimes interchangeable, but capricious suggests motivation by sudden whim or fancy and stresses unpredictability.

an utterly capricious critic

When would fickle be a good substitute for unstable?

The words fickle and unstable can be used in similar contexts, but fickle suggests unreliability because of perverse changeability and incapacity for steadfastness.

performers discover how fickle fans can be

When is inconstant a more appropriate choice than unstable?

The words inconstant and unstable are synonyms, but do differ in nuance. Specifically, inconstant implies an incapacity for steadiness and an inherent tendency to change.

an inconstant friend

When could mercurial be used to replace unstable?

Although the words mercurial and unstable have much in common, mercurial implies a rapid changeability in mood.

made anxious by her boss's mercurial temperament

Example Sentences

Recent Examples of unstable

Research shows that the antioxidant and nutrient content of beets can help protect against oxidative stress, which occurs when there are too many unstable molecules known as free radicals in the body. —Angelica Bottaro, Verywell Health, 29 Jan. 2026

Getting enough vitamin C protects your cells from free radicals, or highly unstable atoms. —Isabel Vasquez Rd Ldn, Health, 29 Jan. 2026

Parts of the country started to return to service over a month later, but telecommunication service remains unstable. —Christine Ro, Forbes.com, 29 Jan. 2026

If the mass is uniform, the disk will be inherently unstable. —Chris Young, Interesting Engineering, 28 Jan. 2026