[adjective](specialized) 64 is an exponential expression (= contains an exponent).(formal) We are looking for exponential growth in our investment (= very fast growth achieved by multiplying the amount of money by itself).(formal) There has been an exponential (= very fast) increase in world population this century.
Meaning of EXPONENTIAL in English
Cambridge English vocab. Кембриджский английский словарь. 2012