Filly (?), n.; pl. Fillies (#). [Cf. Icel. fylia, fr. foli foal. See Foal.] 1. (Zoöl.) A female foal or colt; a young mare. Cf. Colt, Foal.[1913 Webster]
Neighing in likeness of a filly foal.
2. A lively, spirited young girl. [Colloq.] Addison.[1913 Webster]