computational grid
n. A large collection of computers linked via the Internet so that their combined processing power can be harnessed to work on difficult or time-consuming problems.
Instead of analyzing their data on one supercomputer, the Geneva scientists plan to use an Internet-linked network of computers all over the world, which they are calling a computational grid.
—Bill Sanderson, “Web Whizzes Creating Networks Out of Thin Air,” The New York Post, March 12, 2000
It's a simple fact: The average office computer, even though it's powered up 100% of the time, sits idle most of the time.

Reading a Web page, typing a document or analyzing a spreadsheet is not very taxing for your average Pentium-based box. Wouldn't it be nice if you could pool all that horsepower and make it available as a shared network resource to power-hungry applications?

A group of researchers is working on a way to do just that, albeit on a grander scale. Re-searchers from the University of Southern California…demonstrated at Supercomputing 97 (SC97), in San Jose, Calif. last week, a computational grid that used about 3,000 processors in the U.S. and Europe.

The Globus Ubiquitous Supercomputing Testbed (GUSTO) is intended to show how a collection of computers can be strung together across a network to operate like a power grid supplying a neighborhood with electricity.
—Andy Eddy, “Computational grid taps network power,” Network World, December 01, 1997
1997 (earliest)
A computational grid is a hardware and software infrastructure that provides pervasive and dependable access to advanced computational resources. I've chosen the term grid as being analogous to that of an electrical power grid.
—Robert Ward, “Hearing Of The Science, Technology And Space Subcommittee Of The Senate Commerce, Science And Transportation Committee; Subject: Next Generation Internet,” Federal News Service, November 04, 1997