Standard Lemma guide

unstable

adj · verb · 14 senses · updated from the 2026-07-25 local source snapshot

Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.

Sound

Pronunciation

Each Play button uses your device's default local English voice, or a natural local fallback. The selected voice name appears after playback. This is synthesized speech, not a source recording.

  • /ʌnˈsteɪ.bəl/
  • Southern-England: Recorded audio is listed in the source snapshot.
  • rhymes with -eɪbəl
  • CMU ARPABET: AH0 N S T EY1 B AH0 L Digits mark lexical stress: 1 primary, 2 secondary, 0 unstressed.

1

adj

Meaning 1

Not stable.

Definition source: English Wiktionary via Wiktextract

Examples

  • unstable foundation
  • The structure is too unstable to stand safely.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

2

adj

Meaning 2

Having a strong tendency to change.

Definition source: English Wiktionary via Wiktextract

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

3

adj

Meaning 3

Fluctuating; not constant.

Definition source: English Wiktionary via Wiktextract

Examples

  • politically unstable
  • The political situation remains unstable.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

4

adj

Meaning 4

Fickle.

Definition source: English Wiktionary via Wiktextract

Usage: figuratively

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

5

adj

Meaning 5

Unpredictable.

Definition source: English Wiktionary via Wiktextract

Usage: figuratively

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

6

adj

Meaning 6

Readily decomposable.

Definition source: English Wiktionary via Wiktextract

Topics: chemistry, natural-sciences, physical-sciences

Examples

  • chemically unstable

Meaning relationships

Synonyms: none provided

Antonyms: none provided

7

adj

Meaning 7

Radioactive, especially with a short half-life.

Definition source: English Wiktionary via Wiktextract

Topics: natural-sciences, physical-sciences, physics

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

8

verb

Meaning 8

To release (an animal) from a stable.

Definition source: English Wiktionary via Wiktextract

Usage: transitive

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

9

adjective

Meaning 9

lacking stability or fixity or firmness

Definition source: Princeton WordNet 3.0

Examples

  • unstable political conditions
  • the tower proved to be unstable in the high wind
  • an unstable world economy

Meaning relationships

Synonyms: none provided

Antonyms: stable

10

adjective satellite

Meaning 10

subject to change; variable

Definition source: Princeton WordNet 3.0

Examples

  • a fluid situation fraught with uncertainty
  • everything was unstable following the coup

Meaning relationships

Synonyms: fluid

Antonyms: none provided

11

adjective satellite

Meaning 11

affording no ease or reassurance

Definition source: Princeton WordNet 3.0

Examples

  • a precarious truce

Meaning relationships

Synonyms: precarious

Antonyms: none provided

12

adjective satellite

Meaning 12

highly or violently reactive

Definition source: Princeton WordNet 3.0

Examples

  • sensitive and highly unstable compounds

Meaning relationships

Synonyms: none provided

Antonyms: none provided

13

adjective satellite

Meaning 13

disposed to psychological variability

Definition source: Princeton WordNet 3.0

Examples

  • his rather unstable religious convictions

Meaning relationships

Synonyms: none provided

Antonyms: none provided

14

adjective satellite

Meaning 14

suffering from severe mental illness

Definition source: Princeton WordNet 3.0

Examples

  • of unsound mind

Meaning relationships

Synonyms: mentally ill, unsound

Antonyms: none provided

History

Etymology

From Middle English unstable; equivalent to un- (not) + stable.

Etymology tree Proto-Indo-European *h2ent- Proto-Indo-European *-s Proto-Indo-European *h2éntsder. Proto-Germanic *anda- Proto-West Germanic *anda- Old English and- Old English on- Middle English on- English un- English stable English unstable From un- (reversive prefix) + stable.

Across languages

Translations

47 source translations are retained for this English entry.

  • Asturian: inestable — not stable
  • Azerbaijani: sabitsiz — not stable
  • Bulgarian: нестабилен (nestabilen) — not stable
  • Catalan: inestable — not stable
  • Dutch: instabiel — not stable
  • Esperanto: nestabila — not stable
  • Finnish: epävakaa — not stable
  • French: instable — not stable
  • Galician: inestable — not stable
  • Galician: inestábel — not stable
  • Georgian: არამყარი (aramq̇ari) — not stable
  • Georgian: ცვალებადი (cvalebadi) — not stable
  • Georgian: არასტაბილური (arasṭabiluri) — not stable
  • German: instabil — not stable
  • German: labil — not stable
  • Greek: ασταθής (astathís) — not stable
  • Ancient Greek: ἀσταθής (astathḗs) — not stable
  • Ancient Greek: ἀστάθμητος (astáthmētos) — not stable
  • Hindi: अस्थिर (asthir) — not stable
  • Hungarian: instabil — not stable
  • Hungarian: ingatag — not stable
  • Indonesian: labil — not stable
  • Italian: instabile — not stable
  • Japanese: 不安定 (fuantei) — not stable
  • Kazakh: аумалы (aumaly) — not stable
  • Ladino: instavle — not stable
  • Latin: instābilis — not stable
  • Māori: takahuirangi — not stable
  • Māori: whakaroiroi — not stable
  • Māori: koritaka — not stable
  • Persian: ناپایدار (nâpâydâr) — not stable
  • Polish: niestabilny — not stable
  • Polish: niestały — not stable
  • Portuguese: instável — not stable
  • Romanian: instabil — not stable
  • Romanian: inconstant — not stable
  • Romanian: variabil — not stable
  • Russian: неусто́йчивый (neustójčivyj) — not stable
  • Spanish: inestable — not stable
  • Swedish: instabil — not stable
  • Tajik: нопойдор (nopoydor) — not stable
  • French: instable — readily decomposed or decomposable
  • Italian: instabile — readily decomposed or decomposable
  • Northern Kurdish: xwenegir — readily decomposed or decomposable
  • Portuguese: instável — readily decomposed or decomposable
  • Spanish: inestable — readily decomposed or decomposable
  • Spanish: instable — readily decomposed or decomposable
Real reading context

unstable in complete knowledge articles