Twenty-one Definition

twentēwun; often twenēwun
noun
Webster's New World

(card games) Blackjack.

Wiktionary
(sports) A basketball-based game in which players attempt to score exactly twenty-one points.
Wiktionary

Alternative form of twenty-one.

Wiktionary
Synonyms:
numeral

The cardinal number occurring after twenty and before twenty-two, represented in Roman numerals as XXI and in Arabic numerals as 21.

Wiktionary

Alternative spelling of twenty-one.

Wiktionary