An overbearing entity in a specific industry or sphere of activity. A seemingly unbeatable presence always to be reckoned with; whose experience, influence, and skill threatens to defeat competitors with little effort.
In the software industry, Microsoft would be considered the 800-pound gorilla.
The New York Yankees or Manchester United might be considered the 800-pound gorillas of their respective sports.

by xenolon June 19, 2006
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a very strong and/or menacing entity or issue that is obvious but not dealt with
Abuse suffered in prison is an 800-pound gorilla that is undermining justice.
by The Return of Light Joker April 14, 2009
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The big, dominant factor regarding some topic.
“I can’t think of anybody who had more impact than Dr. Dobson,” on rousing evangelicals to the polls, Richard Viguerie, a GOP direct-mail guru, recently told U.S. News & World Report. “He was the 800-pound gorilla.”
by The Wu Factor November 16, 2005
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