1. Astron. zenith distance.
2. zone.
Symbol.
1. the 26th in order or in a series, or, when I is omitted, the 25th.
2. ( sometimes l.c. ) the medieval Roman numeral for 2000. Cf. Roman numerals .
3. Chem. , Physics. atomic number.
4. Elect. impedance.
Z 0
Symbol, Physics. See Z-zero particle .