OS X

UK/əʊˌɛsˈtɛn/US/oʊˌɛsˈtɛn/UK, nonstandard/əʊˌɛsˈɛks/US, nonstandard/oʊˌɛsˈɛks/

proper noun

Former name of macOS; itself formerly known as Mac OS X.

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Meanings

proper noun
  1. trademarkcomputingFormer name of macOS; itself formerly known as Mac OS X.

Origin

Ellipsis of Mac OS X; from OS (“operating system”) + X (“ten”, Roman numeral), as a successor to Mac OS 9.

Full word history & related roots →
Cite this entry
APA

OS X. (n.d.). In WatkinsX Dictionary. Retrieved November 3, 2026, from https://dictionary.watkinsx.com/word/OS%20X

MLA

“OS X.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/OS%20X. Accessed November 3, 2026.

Chicago

WatkinsX Dictionary, s.v. “OS X,” accessed November 3, 2026, https://dictionary.watkinsx.com/word/OS%20X.

Source: OS X on Wiktionary, CC BY-SA 4.0.