Meaning of Z in English

Z

n. (also z) (pl. Zs or Z's) 1 the twenty-sixth letter of the alphabet. 2 (usu. z) Algebra the third unknown quantity. 3 Geom. the third coordinate. 4 Chem. atomic number.

Concise Oxford English dictionary.      Краткий оксфордский словарь английского языка.