adj. (rarer, rarest)
1 seldom done or found or occurring, uncommon, unusual, few and far between.
2 exceptionally good (had a rare time).
3 of less than the usual density, with only loosely packed substance (the rare atmosphere of the mountain tops).
Phrases and idioms:
rare bird = RARA AVIS. rare earth
1 a lanthanide element.
2 an oxide of such an element. rare gas = noble gas.
Derivatives:
rareness n.
Etymology: ME f. L rarus
2.
adj. (rarer, rarest) (of meat) underdone.
Etymology: var. of obs. rear half-cooked (of eggs), f. OE hrer
Useful english dictionary. 2012.