- keep the position warm (1914/1976)
- keep your eye on the ball (1865)
- keystone (1890)
- keystone corner (1891)
- keystoner (1908)
- kick away (1908)
- kill the ball (1888)
- kill the umpire (1872)
- Kingdom of Swat / Old King Swat / King Swat (1901)
- King of Swat (1899)
- knight of the keyboard (1910)
- knockdown pitch (1937)
- knock out of the box (1882)
- knock the cover off the ball (1867)
- knuckle ball (1907)
- knuckleball (1905)
- knuckle curve (1907)
- knuckler (1908)