Emily Dickinson Lexicon

STEAM, n. [Sax. steam, stem; D. stoom.]

1. The vapor of water; or the elastic, aeriform fluid generated by heating water to the boiling point. When produced under the common atmospheric pressure, its elasticity is equivalent to the pressure of the atmosphere, and it is called low steam; but when heated in a confined state, its elastic force is rapidly augmented, and it is then called high steam. On the application of cold, steam instantly returns to the state of water, and thus forms a sudden vacuum. From this property, and from the facility with which an elastic force is generated by means of steam, this constitutes a mechanical agent at once the most powerful and the most manageable, as is seen in the vast and multiplied uses of the steam engine. Steam is invisible, and is to be distinguished from the cloud or mist which it forms in the air, that being water in a minute state of division, resulting from the condensation of steam. D. Olmsted.
2. In popular use, the mist formed by condensed vapor.