Entry 2 senses Webster, 1913 Arroyo /ẽr-oi'-ō/ · Ar·roy·o · IPA /əˈɹɔɪ.oʊ/ 01 n. A water course; a rivulet. pl. Arroyos 1. A water course; a rivulet. 2. The dry bed of a small stream.[Western U. S.]