sliderPronunciation: /ˈslʌɪdə/Definition of slider noun 1a knob or lever which is moved horizontally or vertically to control a variable, such as the volume of a radio. 2 Baseball a pitch that moves laterally as it nears home plate. 3a North American freshwater turtle with a red or yellow patch on the side of the head. Genus Trachemys (or Pseudemys), family Emydidae: several species, in particular the pond slider (T. scripta). slider in other Oxford dictionaries Definition of slider in the US English dictionary