Lewis & Short

mustēla or mustella, ae, f. [mus].

  1. I. A weasel: certum est mustelae posthac numquam credere, Plaut. Stich. 3, 2, 43; cf. Plin. 29, 4, 16, § 60.
  2. II. A fish; acc. to some, a lamprey; acc. to others, an eelpout, Plin. 9, 17, 29, § 63: marina, Enn. ap. App. Mag. p. 299 (Heduph. v. 1 Vahl.).