My 8-pound American Heritage dictionary (fourth edition, 2000) does not acknowledge walkoff as part of the English language. The big book's got Walkman, walk of life, walk-on, walkout, walkover, walk-through, walk-up, even Alice Walker.
But no walkoff -- even though this synthetic ''word" has become as much a part of baseball as the infield fly rule and the designated hitter. Walkoff was first used in reference to game-ending home runs, but now we see headlines and hear commentators talking about walkoff hits, walkoff walks, walkoff balks, walkoff hit-by-pitches, and walkoff errors.
If the game ends with the home team at bat, it's a walkoff win because the beaten visitors are forced to walk off the field in disgrace.
Few of today's major leaguers can remember when they first noticed the new terminology, but there's little doubt ESPN has put walkoff into the mainstream of American sports talk.
And who started the whole thing?
Dennis Eckersley, of course.
''I hate to take credit, but I guess it was me," said the Hall of Fame pitcher who works as a studio commentator for NESN. ''It's not a good thing for a pitcher. You don't want to be known for giving it up. I'd hate to be the one talking about walkoffs like I was the master of 'em."
Hardly. The Eck's Cooperstown resume speaks for itself. But he did happen to give up one of the most memorable walkoffs in history and it was then that his colorful dialect made him the walkoff's mother of invention.
Eckersley and the 1988 A's were ready to close out the first game of the World Series in Los Angeles when Kirk Gibson limped to the plate and hit (by any measure) one of the 10 most famous home runs in baseball history.
Eck was talking walkoff before Gibson.
''Pat Dobson had a word for everything and I started to do that," he said.
Peter Gammons called it DialEck. Eckersley would talk about someone taking him over the bridge (home run). A guy who gave up a lot of homers was a bridgemaster. Money was iron. A particularly speedy fastball had a lot of hair on it. ''Sean McDonough didn't like it when I said that on TV," said Eck.
According to ''The New Dickson Baseball Dictionary," the first walkoff reference appeared July 30, 1988, in the Gannett News Service: ''In Dennis Eckersley's colorful vocabulary, a walkoff piece is a home run that wins the game and the pitcher walks off the mound."
''That's right," Eckersley said this week. ''It was always walkoff piece. Like something you would hang in an art gallery. The walkoff piece is a horrible piece of art.
''The Gibson one had a lot of play in it, but if it wasn't for ESPN, we probably wouldn't have any of this crap."
Today's Sox players agree.
''I can't remember ever hearing it when I was younger," said Jason Varitek, who hit a big-time walkoff piece against Oakland May 11. ''ESPN definitely made it popular."
Kevin Millar, who hit a walkoff the night before Varitek's winner, said, ''There's nothing more exciting than a walkoff. It's the best feeling you can have on a baseball field."
Spotting teammate David Ortiz, the master of the walkoff piece, Millar shouted, ''Papi, how you say 'walkoff' in Spanish?"
Ortiz, who was playing cards with Edgar Renteria, checked with his teammate and concluded that there is no analogous term in Spanish. According to Red Sox Spanish broadcaster Uri Berenguer, ''Cuadrangular que los deja en el terreno" comes closest to capturing the essence of the moment. Hmmm. Not nearly as tidy as walkoff.
Bobby Thomson, Bill Mazeroski, and Carlton Fisk hit the three most famous game-ending homers before the days of the walkoff. When Joe Carter finished the 1993 World Series with a game-winning homer off Mitch Williams, walkoff was creeping into the game's lexicon. According to the Globe library, that's when the word first appeared on these pages -- under Gammons's byline.
''I was there, but I really don't think we called it a walkoff back then," said Sox reliever Mike Timlin. ''It was just a game-winning home run and we were excited to win the World Series."
By the time Aaron Boone won the 2003 American League Championship Series with his moonshot off Tim Wakefield, walkoff was as common as hits, runs, and errors.
Walkoff homer hitters learn to brace themselves for the greeting at home plate. Ortiz, who has made the walkoff his signature play, flips his helmet off as he trots toward home, figuring teammates will go easier on his head if it is not covered by a helmet.
In the May 8 Sunday New York Times magazine, ''On Language" columnist William Safire asked, ''Will the meaning of walk-off [Times style] extend from baseball's game-ending pitch or hit to an adjective in the trope-hungry worlds of politics and business: a career-ending gaffe" or ''an event ending all hope of the competition's victory"?
Indeed, the possibilities are endless. Was Howard Dean's post-Iowa primary speech his walkoff moment? Dan Rather's walkoff pitch was his story on George Bush's military record. Geraldo Rivera should have walked off after the Capone vault fiasco. And does Ben Affleck look back at ''Gigli" and see it the way Eckersley sees his pitch to Gibson? His walkoff movie?
And what about other sports? Wasn't Bobby Orr's overtime, Stanley Cup winner a walkoff goal? Wouldn't Adam Vinatieri's 48-yarder in New Orleans be better remembered as a walkoff piece?
Walkoff. It's the rage. It belongs in the dictionary. It's not going to Walk Away Renee. Walkoff is here to stay.
Dan Shaughnessy is a Globe columnist. His e-mail address is email@example.com.