adj
unstable
uhn-STAY-buhl
adj
1
Likely to shift, collapse, or change suddenly; not firmly fixed.
"The ladder felt unstable, so he climbed down carefully."
"Investors worried about the unstable political situation."
2
Emotionally erratic or prone to sudden mood changes.
"His unstable behaviour worried his close friends."
3
In chemistry or physics, prone to breaking down or decaying, sometimes radioactively.
"The compound is unstable and decomposes quickly at room temperature."
How to Use Unstable
Learner’s notesIn plain EnglishNot steady — physically shaky, emotionally erratic, or chemically prone to breaking down.
Common pairings
unstable ground
emotionally unstable
unstable isotope
politically unstable
Word Forms
more unstable comparative, unstabled past tense, unstables singular, most unstable superlative
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The ladder felt _____, so he climbed down carefully.