public-service corporation

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A corporation providing essential services, such as water or electricity, to the public.

GNU Webster's 1913

1. 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.

WordNet 3.0

1. n. a company that performs a public service; subject to government regulation