RHOPALIUM
Rho*pa"li*um, n.; pl. Rhopalia. Etym: [NL.] (Zoöl.)
Defn: One of the marginal sensory bodies of medusæ belonging to the
Discophora.
RHOPALOCERA
Rhop`a*loc"e*ra, n. pl. Etym: [NL., from Gr. (Zoöl.)
Defn: A division of Lepidoptera including all the butterflies. They differ from other Lepidoptera in having club-shaped antennæ.
RHOTACISM Rho"ta*cism, n. Etym: [Gr. "rwtaki`zein to use the letter r (r) overmuch: cf. F. rhotacisme.]
Defn: An oversounding, or a misuse, of the letter r; specifically (Phylol.), the tendency, exhibited in the Indo-European languages, to change s to r, as wese to were.
RHUBARB Rhu"barb, n. Etym: [F. rhubarbe, OF. rubarbe, rheubarbe, reubarbare, reobarbe, LL. rheubarbarum for rheum barbarum, Gr. Rha (the Volga) on whose banks it grew. Originally, therefore, it was the barbarian plant from the Rha. Cf. Barbarous, Rhaponticine.]
1. (Bot.)
Defn: The name of several large perennial herbs of the genus Rheum and order Polygonaceæ.
2. The large and fleshy leafstalks of Rheum Rhaponticum and other species of the same genus. They are pleasantly acid, and are used in cookery. Called also pieplant.