Pronunciation: (sis'kō), [key]
—pl. (esp. collectively) -co, (esp. referring to two or more kinds or species) -coes, -cos.
any of several whitefishes of the genus Coregonus, of the Great Lakes and smaller lakes of eastern North America.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.