Noun
In general, a place or position with relevant parameters matching other places, as in having the same pressure, chemistry, population etc. Even within a single discipline the parameter might vary according to convenience e.g. in physics alone it might refer to velocity, volume, gravity, and many more. cf. contour, isopleth.
(physics) A line drawn on a graph showing the variation of the pressure of a constant volume of gas as it varies with temperature.
(geology) A contour showing points of equal vertical thickness of strata; equal to an isopach if strata are horizontal.
(genetics) A sequence of DNA that has a reasonably constant proportion of pairs of guanine and cytosine bases, and is rich in genes.
Source: en.wiktionary.org