روث doesn't appear in Hans Wehr's Modern Standard Arabic dictionary, but Lane's Arabic-English Lexicon has 2 entries for it, distinguished by diacritics. Select one below for the full classical Arabic definition.

• رَاثَ Form 1

  1 رَاثَ ذ , (T, S, M, &c.,) aor. يَرُوثُ, (T, A, Msb,) inf. n. رَوْثٌ, (T, M, A, Msb,) said of a horse (S, Msb, K) and the like, (Msb,) [i. e.] of a solid-hoofed animal (T, M, A) of any kind, (T,) He dunged. (M, Msb. *) …

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• رَوْثٌ

  رَوْثٌ ذ , (T, S, M, &c.,) originally an inf. n., (Msb,) The dung (M, Msb *) of the horse (S, Msb, K) and the like, (Msb,) [i. e.] of a solidhoofed animal (T, M, A, Mgh) of any kind: (T, Mgh:) [a coll. gen. n.:] n. un. :…

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