In video games specificly shoot 'em ups of the platform or scrolling variety, a weapon that will destroy every enemy on the screen, or at least do a significant amount of damage. You are given a limited supply, and they are very rare as pickups in most games. Often the only way to get more is to sacrifice a life.

I'm informed by Ashley Pomeroy that the first game to feature smart bombs was Williams' 'Defender', in 1981.

Also the name given to laser-guided bombs used in the Gulf War. The bombardier would drop one of these things while pointing a laser at the thing he wanted to hit, and would watch the bomb cam in his cockpit as the weapon adjusted its fins to hit its target.

During the campaign, a few tapes of these cam transmissions were released to the media, who gave the requisite oohs and aahs at the ability of the Air Force to perform such a surgical strike.

A few years later, it came out that these smart bombs weren't as smart as had been implied. Depending on the specific model, anywhere from 10% to 30% of the bombs failed to hit their targets.