Lewis & Short

rīvālis, e, adj. [rivus].

  1. I. Of or belonging to a brook, brook-: alecula, Col. 8, 15, 6.
    Hence,
  2. II. Subst.: rīvāles, ium, m., those who have or use the same brook, neighbors.
    1. A. Lit.: si inter rivales, id est qui per eundem rivum aquam ducunt, sit contentio de aquae usu, Dig. 43, 20, 1, § 26; 43, 20, 3, § 5; Gell. 14, 1, 4.
    2. B. Trop.: rī-vālis, is, m., one who has the same mistress as another; a competitor in love, a rival: eadem est amica ambobus; plur.: rivales sumus, Plaut. Stich. 3, 1, 30; 5, 4, 47; id. Bacch. Grex 4; Cat. 57, 9.
      Sing., Naev. ap. Charis. p. 214 P. (Com. Rel. p. 10 Rib.); Ter. Eun. 2, 2, 37; 2, 3, 63: militem ego rivalem recipiendum censeo, id. ib. 5, 8, 42; Ov. Am. 2, 19, 60; id. A. A. 2, 539; Suet. Oth. 3 al.
      Abl.: rivale, Ov. R. Am. 791.
      Of animals, Col. 7, 3, 4.
        1. b. Prov.: se amare sine rivali, to be fond of one’s self without a rival, i. e. to be alone in esteeming one’s self: o di, quam ineptus! quam se ipse amans sine rivali! Cic. Q. Fr. 3, 8, 5; so, sine rivali te et tua solus amares, Hor. A. P. 444.