An Eephus pitch (also spelled Ephus) in baseball is a very low speed junk pitch. The delivery from the pitcher has very low velocity and usually catches the hitter off-guard. Its invention is attributed to Rip Sewell of the Pittsburgh Pirates in the 1940s. According to manager Frankie Frisch, the pitch was named by outfielder Maurice Van Robays. When asked what it meant, Van Robays replied, "'Eephus ain't nothing, and that's a nothing pitch." Although the origin is not known for certain, Eephus may come from the Hebrew word "efes" (pronounced "EFF-ess"), meaning "nothing".
The Eephus pitch is thrown overhand like most pitches, but is characterized by an unusual, high arcing trajectory with a peak around 20–25 feet. The corresponding slow velocity bears more resemblance to a slow-pitch softball delivery than to a traditional baseball pitch. It is considered a trick pitch because, in comparison to normal baseball pitches – which run from 70 to 100 miles per hour – an Eephus pitch appears to move in slow motion at 55 miles per hour or less, sometimes into the low-40s.
Development and use in Major League Baseball
After appearing in over 300 major league games, Rip Sewell gave up only one career home run off the Eephus, to Ted Williams in the 1946 All-Star Game. Williams challenged Sewell to throw the Eephus. Sewell obliged, and Williams fouled off the pitch. However, Sewell then announced that he was going to throw the pitch again, and Williams clobbered it for a home run. Years later, however, Williams admitted that he had been running towards the pitcher’s mound as he hit the ball, and photographs reveal that he was in fact a few feet in front of the batter’s box when he made contact. Since under Rule 6.06(a) of the Official Baseball Rules, a batter is out for illegal action when he hits a ball with one or both feet on the ground entirely outside the batter's box, Williams would have been out had it been spotted by the home plate umpire.
Bill "Spaceman" Lee threw an eephus referred to as the "Leephus," "spaceball," or "moon ball." Pitching for the Boston Red Sox in the Game 7 of the 1975 World Series, the Red Sox were up 3–0 when Lee threw three eephus pitches to Tony Pérez with a runner on base. The third resulted in a towering two-run home run and the Red Sox would go on to lose the game 4–3, costing them the chance for their first World Series championship since 1918.
Other pitchers known to have employed the Eephus pitch include: Pedro Borbón, Casey Fossum (called the Fossum Flip), Steve Hamilton of the New York Yankees (the folly floater); Liván Hernández, Phil Niekro; Orlando Hernández, Dave LaRoche (LaLob), Vicente Padilla (dubbed the soap bubble by Vin Scully), Satchel Paige, Pascual Perez (the Pascual Pitch), Kazuhito Tadano, Bob Tewksbury and Carlos Villanueva 
Other nicknames for the Eephus pitch include the balloon ball, blooper ball, gondola, parachute, rainbow pitch – distinct from the rainbow curve, gravity curve, and Bugs Bunny curve, a reference to the Bugs Bunny cartoon where batters swing three times at a pitch before the ball reaches the plate.
- The New York Times baseball blog