public-service corporation

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A corporation providing essential services, such as water or electricity, to the public.

from the GNU version of the Collaborative International Dictionary of English.

• A corporation, such as a railroad company, lighting company, water company, etc., organized or chartered to follow a public calling or to render services more or less essential to the general public convenience or safety.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a company that performs a public service; subject to government regulation