Emily Dickinson Lexicon

DAMP, n.

1. Moist air; humidity; moisture; fog. – Milton.
2. Dejection; depression of spirits; chill. We say, to strike a damp, or to cast a damp, on the spirits. – Milton.
3. [Damps, plur.] Noxious exhalations issuing from the earth, and deleterious or fatal to animal life. These are often known to exist in wells which continue long covered and not used, and in mines and coal-pits; and sometimes they issue from the old lavas of volcanoes. These damps are usually the carbonic acid gas, vulgarly called choke-damp, which instantly suffocates; or some inflammable gas, called fire-damp.