• Webster's Revised Unabridged Dictionary
    • Mesosternum (Anat) The middle portion, or body, of the sternum.
    • Mesosternum (Zoöl) The ventral piece of the middle segment of the thorax in insects.
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Century Dictionary and Cyclopedia
    • n mesosternum In anatomy, the piece or pieces of a breast-bone which has several segments lying between the presternum and the xiphisternum: said chiefly of the segmented sternum of mammals. In man it is the gladiolus or body of the sternum proper, as distinguished from the manubrium and the xiphoid cartilage.
    • n mesosternum In entomology, the ventral or sternal sclerite of the mesothorax; the under side of the mesothorax, opposite the mesonotum.
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Webster's Revised Unabridged Dictionary
Meso-, + sternum,


In literature:

Mesosternum: the underside or breast of the meta-thorax.
"Explanation of Terms Used in Entomology" by John. B. Smith
II, Middle leg and mesosternum.
"Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 4" by Various