volatile

American Heritage® Dictionary of the English Language, Fourth Edition

1. adj. Chemistry Evaporating readily at normal temperatures and pressures.
2. adj. Chemistry That can be readily vaporized.
3. adj. Tending to vary often or widely, as in price: the ups and downs of volatile stocks.
4. adj. Inconstant; fickle: a flirt's volatile affections.
5. adj. Lighthearted; flighty: in a volatile mood.
6. adj. Ephemeral; fleeting.
7. adj. Tending to violence; explosive: a volatile situation with troops and rioters eager for a confrontation.
8. adj. Flying or capable of flying; volant.

Century Dictionary and Cyclopedia

1. Having the power of being readily converted into gas or vapor. Sometimes applied, in chemistry, to those constituents, or that portion, of a substance which is driven off by heating at a specified temperature.
2. Flying, or able to fly; having the power of flight; volant; volitant.
3. Having the quality of taking flight or passing off by spontaneous evaporation; evaporating rapidly; becoming diffused more or less freely in the atmosphere.
4. Lively; brisk; gay; full of spirit; airy; hence, fickle; apt to change: as, a volatile disposition.
5. Transient; not permanent; not lasting.
6. n. A winged creature, as a bird or butterfly.
7. n. Wild fowl collectively.

Wiktionary

1. adj. evaporating or vaporizing readily under normal conditions.
2. adj. explosive.
3. adj. variable or erratic.
4. adj. fickle.
5. adj. temporary or ephemeral.
6. adj. potentially violent.
7. adj. having its associated memory immediately updated with any changes in value.

GNU Webster's 1913

1. adj. Passing through the air on wings, or by the buoyant force of the atmosphere; flying; having the power to fly.
2. adj. Capable of wasting away, or of easily passing into the aëriform state; subject to evaporation.
3. adj. Fig.: Light-hearted; easily affected by circumstances; airy; lively; hence, changeable; fickle.
4. n. A winged animal; wild fowl; game.

WordNet 3.0

1. adj. tending to vary often or widely
2. adj. liable to lead to sudden change or violence
3. adj. marked by erratic changeableness in affections or attachments
4. n. a volatile substance; a substance that changes readily from solid or liquid to a vapor
5. adj. evaporating readily at normal temperatures and pressures