From Latin antrum, from Ancient Greek ἄντρον (ántron, “cave”). Doublet of antre.

• IPA^(key): /ˈæn.tɹəm/

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antrum (plural antrums or antra)

1. (biology) A bodily cavity, especially one having bony walls, especially one in the sinuses.
   • 1964, GFF - Volume 86, page 343:

     In forms with a modified outer antral fence, both this and the adjacent distal band of the domiciliar wall may be concave and form the antrum (Figs. 6 J-K; 7 B), and in some forms the antrum apparently is formed by the dolon alone (dolonal antrum).

• antrum of Highmore

• antral
• antro-

• “antrum”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.
• William Dwight Whitney, Benjamin E[li] Smith, editors (1911), “antrum”, in The Century Dictionary[…], New York, N.Y.: The Century Co., →OCLC.

• Truman, Turman, natrum

From Ancient Greek ἄντρον (ántron, “cave”).

• (Classical Latin) IPA^(key): [ˈan.trũː]
• (modern Italianate Ecclesiastical) IPA^(key): [ˈan.trum]

antrum n (genitive antrī); second declension

1. cave, cavern
   • 29 BCE – 19 BCE, Vergilius, Aeneis 1.166–168:

     Fronte sub adversā scopulīs pendentibus antrum;
     intus aquae dulcēs vīvōque sedīlia saxō:
     nymphārum domus. [...]

     Under the facing cliff [is] a cave with hanging rocks; inside [it], fresh waters and seats in natural stone: a home of nymphs.

2. cavity, hollow
3. tomb

Second-declension noun (neuter).

• “antrum”, in Charlton T. Lewis and Charles Short (1879), A Latin Dictionary, Oxford: Clarendon Press
• “antrum”, in Charlton T. Lewis (1891), An Elementary Latin Dictionary, New York: Harper & Brothers
• "antrum", in Charles du Fresne du Cange, Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)
• “antrum”, in Gaffiot, Félix (1934), Dictionnaire illustré latin-français, Hachette.