Slipperiness

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

Melee

• Flat Zone: the oil slick in the center of the stage.
• Fourside: the surface of the UFO.
• Great Bay: the parts of the turtle's shell not covered by grass.
• Icicle Mountain: many icy platforms.
• Mute City: the pink sections of the track.

Brawl

• Glacial Peak (and its recreation in The Great Maze): various parts of the stage.
• Pokémon Stadium 2: floor of the ice transformation.
• Stage Builder stages: ice blocks are a selectable terrain type.
• Summit: all the icy parts.
• Target Smash!!: level 4 is entirely made of ice.

SSB4

• Flat Zone X: as in Flat Zone, the oil slick.
• Pokémon Stadium 2: as in the Brawl version, the floor of the ice transformation.
• Super Mario Maker: icy blocks, one of the possible random stage elements.

Ultimate

• Flat Zone X: same as in Smash 4.
• Fourside: same as in Melee.
• Pokémon Stadium 2: same as in Brawl.
• Summit: same as in Brawl.
• Super Mario Maker: same as in Smash 4.

Other sources of slipperiness

• Iceberg: turns all platforms slippery.
• Spirits: as a rule, some Spirit Battles turn platforms slippery for the whole match.
• Tingle: as one of the possible effects, Tingle turns all platforms slippery.