Entry 5 senses · 3 variants Webster, 1913 Roach /rōch/ · IPA /ɹoʊt͡ʃ/ n. n. v. t. 01 n. A cockroach. 1. A cockroach.(Zool.) 02 n. A European fresh-water fish of the Carp family (Leuciscus rutilus). It is silver-white, with a greenish back. 1. A European fresh-water fish of the Carp family (Leuciscus rutilus). It is silver-white, with a greenish back.(Zool.) 2. A convex curve or arch cut in the edge of a sail to prevent chafing, or to secure a better fit.(Naut.) Phrases & compounds As sound as a roach — perfectly sound. 03 v. t. To cause to arch. 1. To cause to arch. 2. To cut off, as a horse's mane, so that the part left shall stand upright.