undefined
adjective, noun
undefined is spelled U-N-D-E-F-I-N-E-D: 9 letters and 3 syllables. It appears 1.1 times per million words in written English, the 27,462nd most frequent word form (wordfreq, 2021 data). As an adjective, undefined means “Lacking a definition or value” (English Wiktionary, September 2026).
How many letters and syllables are in undefined?
| Letters | 9: U-N-D-E-F-I-N-E-D |
|---|---|
| Syllables | 3 (from its American pronunciation) |
| In writing | 1.1 times per million words; the 27,462nd most frequent word form |
| Wrong spellings searched | none measured in search |
Sources: letters and syllables from the English Wiktionary's hyphenation or pronunciation and the CMU Pronouncing Dictionary; written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How common is undefined?
Undefined appears 1.1 times per million words in written English, the 27,462nd most frequent word form in the list.
Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How do you pronounce undefined?
- US
Undefined has 3 syllables (counted from its American pronunciation in the CMU Pronouncing Dictionary).
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract). Recordings: LL-Q1860_(eng)-Flame,_not_lame-undefined.wav, Wikimedia Commons (author and licence on each file's page).
Forms of undefined
- undefineds plural
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
What does undefined mean?
The meanings the English Wiktionary records, quoted as written there (source below).
adjective
- 1
Lacking a definition or value.
- 2
That does not have a logically sound meaning within a specific formal system and is thus not assigned an interpretation.
The result of division by zero is undefined.
- 3
That behaves unreliably due to dependence on an uninitialized value or inconsistently ported code.
In C, relying on a variable's value right after a malloc call is undefined behvaior.
noun
- 1
An undefined value.
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
How do you abbreviate undefined?
Wiktionary records one abbreviation of undefined: undef.
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
Undefined in Spanish, French, German and Portuguese
In the sense lacking definition or value:
| Language | Words |
|---|---|
| French | indéfini |
| Portuguese | indefinido |
| Spanish | indefinido |
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract). Translations are Wiktionary's, by sense; a linked word has its own PlainSpell page.
Where does undefined come from?
From un- + defined.
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).