1. A localized high heat-flow region with a deep cause, often associated with volcanism and other geothermal activity. Hawaii and Yellowstone are presumably hot spots. The hot-spot hypothesis uses hot spots as a fixed reference frame for determining plate motion with respect to them. 2. An image region that records a large amount of backscattered solar radiation. 3. A specular reflection of the sun. 4. A bright spot hydrocarbon indicator (q.v.).