Entry 2 senses · 2 variants Webster, 1913 Coss /(kŏs)/ · IPA /kɒs/ n. n. 01 n. A Hindoo measure of distance, varying from one and a half to two English miles. 1. A Hindoo measure of distance, varying from one and a half to two English miles. 02 n. A thing (only in phrase below). 1. A thing (only in phrase below). Phrases & compounds Rule of Coss — an old name for Algebra. [It. regola di cosa rule of thing, the unknown quantity being called the cosa, or the thing.]