Originally Posted by
Ray-Chill
Despite the precise definition of steam (taken literally it is something that we cannot see) it is normal usage here (at least) to refer to kettles steaming, wet clothes steaming, sweaty people steaming, and so on. We also talk about windows or spectacles being steamed up. The stuff we can see may not, strictly speaking, be steam, but that's what we call it.
However, that stuff coming out of your mouth on a winter's morning is breath.
Just like the stuff you're peeing out is called piss.