1.  26th letter of the alphabet; unknown, variable (mathematics). zz (zē; in england commonly, and in america sometimes, z&ebreve;d; formerly, also, &ibreve;zz&ebreve;rd) z, the twenty-sixth and last letter of the english alphabet, is a vocal consonant. it is taken from the latin letter z, which came from the greek alphabet, this having it from a semitic source. the ultimate origin is probably egyptian. etymologically, it is most closely related to s, y, and j; as in glass, glaze; e. yoke, gr. , l. yugum; e. zealous, jealous. see: guide to pronunciation, aâ§aâ§ 273, 274.z n