Did you know?

Click any word in a definition or example to find the entry for that word

unstable - definition and synonyms

What are red words?

90% of the time, speakers of English use just 7,500 words in speech and writing. These words appear in red, and are graded with stars. One-star words are frequent, two-star words are more frequent, and three-star words are the most frequent.

Thesaurus diagram

The thesaurus of synonyms and related words is fully integrated into the dictionary. Click on the thesaurus category heading under the button in an entry to see the synonyms and related words for that meaning.

adjective     unstable pronunciation in American English
  1. 1
    an unstable person becomes angry or upset often and very suddenly

    My father wasn’t a bad man, but he was emotionally unstable.

  2. 3
    an unstable system, situation, or relationship often has serious problems

    an unstable economy

  3. 4
    chemistry an unstable substance reacts very easily with other chemical substances and can be dangerous
  4. 6
    physics an unstable object is likely to move or change because of the forces affecting it


a lifestyle focussing on simple pleasures such as comfort and cosiness in the home, and spending time with friends and family

BuzzWord Article

Open Dictionary


a form of location that involves the underwater detonation of a bomb which causes sound waves that are picked up by ships

add a word


A must for anyone with an interest in the changing face of language. The Macmillan Dictionary blog explores English as it is spoken around the world today.

global English and language change from our blog
Macmillan learn live love play