rara avis [ˈrɛərə ˈeɪvɪs] n.
1.) A person of a type seldom encountered; an exceptional person, a paragon. Occas. without article.
2.) That which is seldom found; an unusual occurrence, etc.; something very remarkable.
3.) lit. A rare bird (O.E.D. 2nd Ed.).
Etymology: Latin rara avis : rara, feminine of rarus, rare + avis, bird.
"Sit formosa decens dives fecunda, vetustos
porticibus disponat avos, intactior omni
crinibus effusis bellum dirimente Sabina,
rara avis in terris nigroque simillima cycno:
quis feret uxorem cui constant omnia?"
(Satura, Decimus Junius Juvenalis, ~100).
"Suppose her free from strife,
Rich, fair, and fruitful, of unblemish'd life;
Chaste as the Sabines, whose prevailing charms
Dismiss'd their husbands, and their brother's arms:
Grant her, besides, of noble blood that ran
In ancient veins ere heraldry began:
Suppose all these, and take a poet's word,
A black swan is not half so rare a bird.
A wife, so hung with virtues, such a freight,
What mortal shoulders could support the weight!"
(The Satires of Decimus Junius Juvenalis, John Dryden (trans.), 1693).