—n. 1. a cardinal number, 10 times 2.
2. a symbol for this number, as 20 or XX.
3. a set of this many persons or things.
4. Informal.a twenty-dollar bill: Can you give me two tens for a twenty? 5. twenties,the numbers, years, degrees, or the like, from 20 through 29, as in referring to numbered streets, indicating the years of a lifetime or of a century, or referring to degrees of temperature: He lives in the West Twenties. She's in her early twenties. The temperature must be in the high twenties today.