Sixty \Six"ty\, a. [AS. siextig; akin to G. sechzig, Goth. sa['i]hs tigjus. See Six, Ten, and cf. Sixteen.] Six times ten; fifty-nine and one more; threescore.
Source: Webster's Revised Unabridged Dictionary (1913)
Sixty \Six"ty\, n.; pl. Sixties.1. The sum of six times ten; sixty units or objects.
2. A symbol representing sixty units, as 60, lx., or LX.