You are thinking of Sir Barnes Wallis' famous "bouncing bomb". He also designed the super-heavy "Tallboy" and "Grand Slam" bombs which were also carried by the Lancaster.
"Skip bombing" is a method of bomb release at very low altitude and high speed, designed to make the bomb "skip" off the impact surface(water or hard ground), making it easier to hit targets with a small planform area but a relatively large side area, eg: ships.