I. noun
1. : a place that is hotter than the surrounding surface: as
a. : a spot in the intake manifold of an internal-combustion engine which is heated by the exhaust gases to aid in the vaporization of the fuel
b. : an overheated spot in the combustion chamber tending to cause preignition
c. : a place in the shell of a furnace hotter than the rest
d. : an uncooled portion of a combustion chamber against which a charge is sprayed for ignition in a semidiesel engine
2. : a region of high forest-fire frequency
3.
a. : an area in a plastered wall containing alkaline salts that cause paper and paints to discolor
b. : an area on a negative or print representing excessive illumination of a part of the subject
c. : an area of excessive illumination (as on a subject or on the easel of an enlarger) in a pictorial reproduction
4. : a center of night life : nightclub
II. noun
1. : a place in the upper mantle of the earth at which hot magma from the lower mantle upwells to melt through the crust usually in the interior of a tectonic plate to form volcanic features ; also : a place in the crust overlying a hot spot
2. : an area of political, military, or civil unrest usually considered dangerous