Definition of koppa:
(n) :
The Greek numeral Ϟ (lowercase ϟ), descended from the ancient letter and having the numerical value of 90.
(n) :
The archaic Cyrillic numeral Ҁ (lowercase ҁ), descended from the ancient Greek letter and having the numerical value of 90.
(n) :
An Ancient Greek letter representing /k/, Ϙ / ϙ, replaced by kappa by the Classical Greek period.