flash point

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The lowest temperature at which a combustible liquid or solid produces sufficient vapor near its surface to generate an ignitable mixture with air.
• noun The point at which eruption into significant action, creation, or violence occurs.

from The Century Dictionary.

• noun Same as flashing-point.

from the GNU version of the Collaborative International Dictionary of English.

• noun the lowest temperature at which the vapors given off by a volatile liquid exposed to air will burst into flame when approached by a flame. Also called flashing point.
• noun That point in time or that degree of provocation at which someone will suddenly begin to act vigorously; -- often used in reference to angry reactions.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The lowest temperature at which a liquid can form an ignitable mixture in air near the surface of the liquid.
• noun figuratively A hotspot; a dangerous place of violent political unrest

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the lowest temperature at which the vapor of a combustible liquid can be ignited in air
• noun point at which something is ready to blow up
• noun the lowest temperature at which the vapor of a combustible liquid can be ignited in air
• noun point at which something is ready to blow up