hypostasis
noun
hy·pos·ta·sis hī-ˈpä-stə-səs 
plural hypostases hī-ˈpä-stə-ˌsēz
1
a
: something that settles at the bottom of a fluid
b
: the settling of blood in the dependent parts of an organ or body
2
: person sense 3
3
a
: the substance or essential nature of an individual
b
: something that is hypostatized
4
: failure of a gene to produce its usual effect when coupled with another gene that is epistatic toward it
hypostatic
ˌhī-pə-ˈsta-tik
adjective hypostatically
ˌhī-pə-ˈsta-ti-k(ə-)lē
adverb 
Word History
Etymology
Late Latin, substance, sediment, from Greek, support, foundation, substance, sediment, from hyphistasthai to stand under, support, from hypo- + histasthai to be standing — more at stand
First Known Use
1590, in the meaning defined at sense 1a
Medical Definition
hypostasis
noun
hy·pos·ta·sis hī-ˈpäs-tə-səs
plural hypostases -ˌsēz
1
: the settling of blood in relatively lower parts of an organ or the body due to impaired or absent circulation
the face was discolored by postmortem hypostasis
2
: failure of a gene to produce its usual effect when coupled with another gene that is epistatic toward it