Colossus Death is a method of destroying enemies because of the death of the dying experimental. As they fall to the ground they crush anything beneath them doing tremendous damage. Most units will be instantly destroyed by this. This tactic is very inefficient and should only be used if you need to get rid of some Galactic Colossus's or you have tons of resources to spare!
The Sacred Assault Bot can also crush units (see massive) by walking over them and also does not require the death of a potential game-ender (and you can blast enemies too far away to step on with your laser)
See Air Crash for related information.