The first comprehensive revision of the Oxford English Dictionary - a 20-volume edition weighing nearly 140 pounds - unveiled Wednesday contains such medical and business terms as "Amex" and the AIDS virus "HIV."

"For me this is like being present at the second revelation of the Bible," former Librarian of Congress Emeritus Daniel Boorstin said at the unveiling of the new edition at a London hotel.Brought right up to date with "yuppification," the last word added in the 21,728-page new edition, the full set costs $2,500 and takes up 44 inches of shelf space.

Some of the words are like small novels themselves. The longest entry, says co-editor John Simpson, is "pneumonoultramicroscopicsilicovolcanoconiosis," a miner's lung disease.

The dictionary is the culmination of five years of work by a team of 36 lexicographers at Oxford University Press headquarters, 50 miles west of London, as well as researchers and computer scientists in Canada and the United States.

The first edition of the Oxford English Dictionary was begun in 1884 by Scottish schoolmaster James Murray, but he died at age 78 in 1915 when the dictionary had reached "Ta-."

It was completed in 1928 and supplements have been added, but the new edition is the first comprehensive revision of the original.

Project director Timothy Benbow said "the development of the software for an electronic version of the text" was a major achievement of the new version.

A computer disc containing the entire first edition of the dictionary has been available for a year on software programmed by the University of Waterloo, Columbia, Canada. The second edition will be available on disc by 1991, enabling a word-search that would have taken hours to be completed in seconds.