Intangibility was a super power that allowed a character to become untouchable, making any one attempting to touch them simply pass through them. This ability can be associated with Density Control, in which a person can lower their density so much that it allows them to pass through solid matter. The ability is also associated with phasing.
The ability could also be associated with ones' ability to transform into gaseous matter, such as steam. Characters with this ability are not completely unstoppable, but many times harder to defeat, for example, if someone were to try and shoot a bullet from a revolver at such a character, the bullet would simply pass through them without harming them, however, in some cases, a character in a gaseous state could still be affected by other gases. Superman for example, could use his super breath and blow them into a sealed bottle, making it impossible to escape.