z-axis
— Noun
– English
～ the third axis in a 3-dimensional coordinate system
z
— Noun
– English
～ the ending of a series or sequence; "the Alpha and the Omega, the first and the last, the beginning and the end"--Revelation
Z
— Noun
– English
～ the 26th letter of the Roman alphabet; "the British call Z zed and the Scots call it ezed but Americans call it zee"; "he doesn't know A from izzard"