In nonstandard analysis, a branch of mathematics, overspill (referred to as overflow by Goldblatt (1998, p. 129)) is a widely used proof technique. It is based on the fact that the set of standard natural numbers N is not an internal subset of the internal set * N of hypernatural numbers.

Signal overspill is the receiving of a broadcast signal outside of its geographical target area. Radio frequencies have no way of obeying geographical borders and licensing arrangements, and the extent of overspill depends on where broadcast transmitters are sited and their power.