What is a bitonic function?

Excuse me, could you please elaborate on what a bitonic function is? I'm familiar with basic mathematical concepts, but this term seems a bit unfamiliar to me. Is it a specific type of function used in cryptography or financial analysis? If so, could you provide an example of how it might be applied in either of those fields? I'm curious to learn more about its unique properties and how it differs from other functions commonly used in those areas. Thank you for your time.