steam / stēm/ • n. the vapor into which water is converted when heated, forming a white mist of minute water droplets in the air. ∎  the invisible gaseous form of water, formed by boiling, from which this vapor condenses. ∎  the expansive force of this vapor used as a source of power for machines: the equipment was originally powered by steam | [as adj.] a steam train. ∎  locomotives and railroad systems powered in this way: the last years of steam. ∎ fig. energy and momentum or impetus: the anticorruption drive gathered steam.• v. 1. [intr.] give off or produce steam: a mug of coffee was steaming at her elbow. ∎  (steam up or steam something up) become or cause to become covered or misted over with steam: [intr.] the glass keeps steaming up | [tr.] the warm air had begun to steam up the windows. ∎  (often be/get steamed up) inf. be or become extremely agitated or angry: you got all steamed up over nothing! after steaming behind the closed door in his office, he came out and screamed at her.2. [tr.] cook (food) by heating it in steam from boiling water: steam the vegetables until just tender. ∎  [intr.] (of food) cook in this way: add the mussels and leave them to steam. ∎  clean or otherwise treat with steam: he steamed his shirts in the bathroom to remove the wrinkles. ∎  apply steam to (something fixed with adhesive) so as to open or loosen it: he'd steamed the letter open and then resealed it. ∎  operate (a steam locomotive).3. [intr.] (of a ship or train) travel somewhere under steam power: the 11:54 steamed into the station. ∎ inf. come, go, or move somewhere rapidly or in a forceful way: Jerry steamed in ten minutes late | fig. the company has steamed ahead with its investment program. PHRASES: pick up (or get up) steam1. generate enough pressure to drive a steam engine.2. (of a project in its early stages) gradually gain more impetus and driving force: his campaign steadily picked up steam.have steam coming out of one's ears inf. be extremely angry or irritated.in steam (of a steam locomotive) ready for work, with steam in the boiler.let (or blow) off steam inf. (of a person) get rid of pent-up energy or strong emotion.run out of (or lose) steam inf. lose impetus or enthusiasm: a rebellion that had run out of steam.under one's own steam (with reference to travel) without assistance from others: we're going to have to get there under our own steam.under steam (of a machine) being operated by steam.