steam1 W3 [uncountable]
the hot mist that water produces when it is boiled:
Steam rose from the hot tub.
the mist that forms on windows, mirrors etc when warm wet air suddenly becomes cold
mist on surfaceD
power that is produced by boiling water to make steam, in order to make things work or move:
The engines are driven by steam.
steam engine/train/hammer etc (=an engine etc that works by steam power)
to get rid of your anger, excitement, or energy in a way that does not harm anyone by doing something active
5 also gather/gain steam
if an engine picks up steam, it gradually starts to go faster
if plans, beliefs etc pick up steam, they gradually become more important and more people become interested in them:
The election campaign is picking up steam.
6 also lose steam
to no longer have the energy or the desire to continue doing something, especially because you are tired:
I usually just let her yell until she runs out of steam.
if you go somewhere under your own steam, you get there without help from anyone else:
I'll get to the restaurant under my own steam.
a railway system in which the trains use steam for power:
the age of steam