zeal·ous \ˈzeləs\adjective Etymology: Medieval Latin zelosus, from Late Latin zelus zeal + Latin -osus -ose : filled with or characterized by zeal : warmly engaged or ardent especially in behalf of something : marked by a fervent partisanship for a person, a cause, or an ideal < a zealous supporter of the Confederacy — D.Y.Thomas > < impetuous in his enthusiasm, zealous for liberty — G.H.Genzmer >