Meaning of Z in English
(plural Z's or Zs), z (plural z's or zs) [noun] [C] - the 26th and last letter of the English alphabet(US informal) If you catch/get/make some/a few z's, you sleep."Do you want to come back for a drink after the film?" "No thanks, I need to go home and catch some z's."
Cambridge English vocab. Кембриджский английский словарь. 2012