¦ noun
1. the hot vapour into which water is converted when heated, which condenses in the air into a mist of minute water droplets.
2. the expansive force of this vapour used as a source of power for machines.
3. momentum; impetus: the dispute gathered steam.
¦ verb
1. give off or produce steam.
(steam up or steam something up) become or cause something to become misted over with steam.
2. cook (food) by heating it in steam from boiling water.
clean or otherwise treat with steam.
apply steam to (something fixed with adhesive) so as to open or loosen it.
3. (of a ship or train) travel somewhere under steam power.
informal come, go, or move somewhere rapidly or in a forceful way.
generate steam in and operate (a steam locomotive).
4. (be/get steamed up) informal be or become extremely agitated or angry.
Phrases
get up (or pick up) steam
1. generate enough pressure to drive a steam engine.
2. (of an activity, project, etc.) gradually gain impetus.
have steam coming out of one's ears informal be extremely angry.
let (or blow) off steam informal get rid of pent-up energy or strong emotion.
run out of (or lose) steam informal lose impetus or enthusiasm.
under one's own steam without assistance from others.
Origin
OE steam 'vapour', steman 'emit a scent, be exhaled', of Gmc origin.