(mathematics, of a function) Having the property that the same argument may yield multiple values, but different arguments never yield the same value.
(mathematics,logic, of a relationship between two sets) having the property that an element of one set may be assigned by the relationship to several elements in the other set, but that a given element in the second set can have only one member of the first set assigned to it.
"Being a genetic mother of" is a one-to-many relation from the set of cats to the set of cats.
From a single source to multiple recipients.
Traditional mass media, both print and broadcast, are forms of one-to-many communications.