Wiktionary
n. (context planetology English) An exosolar planet whose characteristics are similar to Jupiter, but which orbits its parent star much more closely and thus has higher temperatures.
Wikipedia
Hot Jupiters (also called roaster planets, epistellar jovians, pegasids or pegasean planets) are a class of exoplanets that are inferred to be physically similar to Jupiter but that have very short orbital radii with semi-major axes from . The close proximity to their stars and high surface temperatures resulted in the moniker "hot Jupiters".
Hot Jupiters are the easiest extrasolar planets to detect via the radial-velocity method, because the oscillations they induce in their parent stars' motion are relatively large and rapid compared to those of other known types of planets. One of the best-known hot Jupiters is 51 Pegasi b. Discovered in 1995, it was the first extrasolar planet found orbiting a Sun-like star. 51 Pegasi b has an orbital period of about 4 days.
Usage examples of "hot jupiter".
With its anchoring cable severed, the Post was beginning to sink away from its design altitude, deeper into the roiling murk of the hot Jupiter's atmosphere.