meso-

1. a combining form meaning “middle,” used in the formation of compound words: mesocephalic.

combining form

1. middle or intermediatemesomorph

word-forming element meaning “middle, intermediate, halfway,” sometimes mes- before vowels, comb. form of Greek mesos “middle, in the middle; middling, moderate; between” (see medial (adj.)). pref.

1. In the middle; middle:mesoderm.
2. Intermediate:mesomere.
3. Mesentery:mesoileum.
4. Characterizing a superimposable isomer:meso-2,3-dichlorobutane.