exponential

Short definition from Wiktionary

Adjective

1. 1
   Relating to an exponent.
2. 2
   Expressed in terms of an exponent (power of a base), the base often being 10 or e.
3. 3
   Characterised by a rate of change that is proportional to the value of the varying quantity, or, equivalently, by a doubling or halving over successive fixed intervals of time or other parameter, described as exponential growth or exponential decay.
4. 4
   Characterised by a very rapid rate of change, especially increase, or merely a very large amount or degree.

Noun

1. 1
   Any function that has an exponent as an independent variable.