head of steam

English

Etymology

From the need of the boiler of a steam locomotive to exceed a minimum amount of pressure before the locomotive could start moving. (See head (“buildup of fluid pressure”), also pressure head.)

Pronunciation

Audio (AU) (file)

Noun

head of steam (plural heads of steam)

(idiomatic) A significant amount of energy, vigour or momentum, sufficient to make progress or succeed in a task.
- 2011 January 25, Paul Fletcher, “Arsenal 3 - 0 Ipswich (agg 3 - 1)”, in BBC‎:
  Arsenal were starting to work up a head of steam and Tractor Boys boss Paul Jewell cut an increasingly frustrated figure on the touchline.