Z1

noun (plural Zs or Z's)

• 1the twenty-sixth letter of the alphabet.
• denoting the next after Y in a set of items, categories, etc..
• denoting a third unknown or unspecified person or thing:X sold a car to Y (a car dealer) who in turn sold it to Z (a finance company)
• (usually z) the third unknown quantity in an algebraic expression.

  [the introduction of x, y, and z as symbols of unknown quantities is due to Descartes (see X¹)]
• (usually z) denoting the third axis in a three-dimensional system of coordinates: [in combination]:the z-axis

• 2a shape like that of a capital Z: [in combination]:the Z-shaped crack in the paving stone

• 3used in repeated form to represent the sound of buzzing or snoring:this weather has sucked all the energy out of me ... zzzz