Onus probandi (ō´nus pro-ban´).—The burden of proving (legal).

Optimates (op-ti-mā´tēs).—Aristocrats. Literally, the best. In ancient times the aristocracy was composed of men selected for their superior vigor as the best in the tribe.

Opum furiosa cupido—Ovid (op´um furi-ō´sa ku-pī´).—The ungovernable greed for wealth.

Ora et labora (ōr´ā et lab-ōr´ā).—Pray and work.

Ora pro nobis (ōr´ā pro nō´bis).—Pray for us. The words of the refrain of the well-known hymn in the Roman Catholic mass.

Ore rotundo (ōr´ē rō-tun´).—With round, full voice.

O tempora! O mores!—Horace (tem´por-a mor´ēz).—O the times! O the manners!

Otium cum dignitate (ō´shi-um kum dig-ni-tā´te).—Ease with dignity.

Otium sine dignitate (sin´e).—Ease without dignity.

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