combining form
or meso-
Etymology: Latin, from Greek, from mesos — more at mid
1.
a. : in the middle : intermediate (as in position, size, type, time, degree)
meso derm
mes odont
meso nephroma
meso plankton
meso prosopic
Meso zoa
meso carp
b. : mesentery or membrane supporting a (specified) part
meso caecum
meso colon
mes archium
c. : mesoderm : mesodermal and
mes ameboid
2. meso- : a reduction product of a porphyrin or other pyrrole derivative in which one or more vinyl groups have been hydrogenated to ethyl
meso hemin
meso bilirubin
3. : an inorganic acid regarded as an intermediate hydrated form
di meso periodic acid H 4 I 2 O 9
4. meso- , usually italic
a. : an optical isomer whose inactivity is attributed to the molecule's being internally compensated
meso -tartaric acid
b. : a middle position or group especially in a cyclic compound
meso -chloro-anthracene is 9-chloro-anthracene
meso -phenyl-imidazole is 2-phenyl-imidazole
— abbr. ms or μ
5. : of late Paleozoic or of Mesozoic age — in names of igneous rocks