unstable
adjective
un·sta·ble
ˌən-ˈstā-bəl 
: not stable : not firm or fixed : not constant: such as
a
: not steady in action or movement : irregular
an unstable pulse
b
: wavering in purpose or intent : vacillating
c
: lacking steadiness : apt to move, sway, or fall
an unstable tower
d(1)
: liable to change or alteration
an unstable economy
unstable weather
(2)
: readily changing (as by decomposing) in chemical or physical composition or in biological activity
e
: characterized by lack of emotional control
unstableness
noun
Examples of unstable in a Sentence
an unstable nuclear reactor core
the minute we put the books down on the unstable desk, the whole stack went crashing to the floor
Recent Examples on the Web
Sitting places the glutes in a lengthened, inactive state that pushes the pelvis forward and puts the lower back at a painfully compressed, mechanical disadvantage, which in turn creates a posture that feels tight, stiff and unstable.
—
Dana Santas, CNN Money, 30 May 2025
Business models are under pressure, distribution is unstable, and competition for attention is fiercer than ever.
—Todd Spangler, Variety, 29 May 2025
The mountain side of the glacier had been unstable since last week, when millions of pounds of rock debris fell onto the glacier surface, Davies said.
—Julia Jacobo, ABC News, 29 May 2025
If a poor single woman who came to New York to work in an unstable low-wage job became pregnant out of wedlock, shame, stigma, poverty, lack of childcare options, and the anonymity of city living might lead her to leave her infant on a stoop.
—Time, 28 May 2025
See All Example Sentences for unstable
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Dana Santas, CNN Money, 30 May 2025
Business models are under pressure, distribution is unstable, and competition for attention is fiercer than ever.
—Todd Spangler, Variety, 29 May 2025
The mountain side of the glacier had been unstable since last week, when millions of pounds of rock debris fell onto the glacier surface, Davies said.
—Julia Jacobo, ABC News, 29 May 2025
If a poor single woman who came to New York to work in an unstable low-wage job became pregnant out of wedlock, shame, stigma, poverty, lack of childcare options, and the anonymity of city living might lead her to leave her infant on a stoop.
—Time, 28 May 2025
See All Example Sentences for unstable
Cite this Entry
“Unstable.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/unstable. Accessed 6 Jun. 2025.
Copy CitationKids Definition
unstable
adjective
un·sta·ble
ˌən-ˈstā-bəl
ˈən-
1
: not stable : not firm or fixed : fluctuating
unstable prices
an unstable tower
unstable weather
2
: readily changing in chemical composition or physical state or properties (as by breaking down into parts)
an unstable atomic nucleus
Medical Definition
unstable
adjective
un·sta·ble
-ˈstā-bəl
: not stable: as
a
: characterized by frequent or unpredictable changes
a patient in unstable condition
b
: readily changing (as by decomposing) in chemical composition or biological activity
unstable compounds
c
: characterized by lack of emotional control or stability
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