An umbrella term is a word that provides a superset or grouping of related concepts, also called a hypernym. For example, cryptology is an umbrella term that encompasses cryptography and cryptanalysis, among other fields. Similarly, an "umbrella organization" can be an organization which is a central and coordinating body representing a number of smaller, separate bodies.
Editors of Random House. Random House Webster's College Dictionary, Eds. of Random House, (Random House, New York), c 1992,1991. With various: Indices, Tables, Guides, etc., 1568 pgs.