Slipperiness

Slippery (sometimes referred to as slick, or ice physics) is a term used to describe certain platforms or floors throughout the  series on which characters can slide and have less traction than normal. In Super Smash Bros. Brawl, slippery platforms significantly increase the chances of prat falling.

The Ice Climbers have the unusual property of being able to walk along the ice with no loss of traction, but otherwise have lower traction on regular floors. Luigi from Smash 64 to Smash 4 and Mii Gunner in Ultimate have the worst traction in their respective games, which bodes well for them in certain aspects of competitive play.

Stages with slippery platforms

 * Brinstar Depths: the surface of the pipe structures.
 * Flat Zone: the oil slick in the center of the stage.
 * Flat Zone X: as in Flat Zone, the oil slick.
 * Fourside: the surface of the UFO.
 * Great Bay: the parts of the turtle's shell not covered by grass. Melee only.
 * Icicle Mountain: the ice platforms.
 * the areas of the track.
 * Pokémon Stadium 2: floor of the ice transformation.
 * Summit: the stage takes place on an iceberg.
 * Super Mario Maker: the ice blocks, one of the possible random stage elements.

Other sources of slipperiness

 * The Ice Climbers' Final Smash, Iceberg, temporarily makes the floor slippery.
 * The Tingle Assist Trophy in Brawl and Smash 4 temporarily turns the floor slippery as one of the many random effects.
 * The Glacial Peak (and its recreation in The Great Maze) in the The Subspace Emissary. The fight after climbing atop the mountain takes place on 3 ice structures.
 * The Stage Builder features ice blocks as a selectable terrain type in every game it appears, excluding Smash 4.
 * The fourth level from Brawl's Target Smash!! is entirely made of ice.
 * In Ultimate, some Spirit Battles turn the floor slippery for the whole match.