n (Geological Science) geology a line on a map connecting points below which a particular rock stratum has the same thickness[C20: from iso- + Greek pakhus thick, pakhutēs thickness]
i•so•pach
(ˈaɪ səˌpæk)
n. a line drawn on a map connecting all points of equal thickness of a particular geologic formation. [1915–20; iso- + -pach < Greek páchos thickness]i`so•pach′ous,adj.