The Body Slam, or Belly Flop, is one of Crash's moves. To perform it, the player must jump and press the duck button ( in PlayStation games) while in the air. Crash will slam down and crush anything beneath him. It was first used in Crash Bandicoot 2: Cortex Strikes Back.
The Body Slam can destroy locked crates (although the Super Charged Body Slam is needed to do this in Crash Bandicoot: Warped). Other than that, it doesn't have many uses. It can also be used to gain slightly more height from a jump, albeit less than the Double Jump in Warped.
The Belly Flop's Power-Up is the Super Charged Body Slam. It increases the radius of the Belly Flop by two or three crates.
Crash uses the Body Slam in Crash Bandicoot: Dansu! De Jump! Na Daibouken to try and impress Aku Aku and to 'clean' Ripper Roo's books. Instead of referring to it as the 'Body Slam', Crash calls it the 'Body Press'.