Definitions of steam on the Web:
In physical chemistry and in engineering, steam refers to vaporized water. It is a pure, invisible gas (for mist see below), which at standard atmospheric pressure often has a temperature of around 100 degrees celsius, and occupies about sixteen hundred times the volume of liquid water (steam can of course be much hotter than the boiling point of water; such steam is usually called superheated steam).
en.wikipedia.org/wiki/Steam
ok, wikipedia.org does not mean the definition is correct :-)
The vapor phase of water, unmixed with other gases.
www.cleaver-brooks.com/GlossRW.html
Water vapor at a temperature greater than the boiling point.
amsglossary.allenpress.com/glossary/browse
The invisible vapor into which water is converted when it boils.
park.org/Philippines/pinatubo/page7.html
Visible mixture of condensation and water vapor in air. Product of boiling water.
http://www.stuffintheair.com/Blowin_...ogWeather.html
If it is not water vapor, what else can it be?
As I see it, it is very hot H2O.