Wiktionary
integral equation
n. (context mathematics English) An equation involving a function and integrals of that function to be solved for
Wikipedia
Integral equation
In mathematics, an integral equation is an equation in which an unknown function appears under an integral sign.
There is a close connection between differential and integral equations, and some problems may be formulated either way. See, for example, Green's function, Fredholm theory, and Maxwell's equations.