x 1 or X 
(ĕks)
(ĕks)n. pl. x's or X's also xs or Xs
1. The 24th letter of the modern English alphabet.
2. Any of the speech sounds represented by the letter x.
3. The 24th in a series.
4. Something shaped like the letter X.
5. A mark inscribed to represent the signature of one who is unable to sign one's name.
6. An unknown or unnamed factor, thing, or person.
tr.v. x'd, x'ing, x's or X'd or X'ing or X's
1. To mark or sign with an X.
2. To delete, cancel, or obliterate with a series of X's. Often used with out.
roman numerals, SundialSundials indicate the time of day when a pointer casts a shadow onto a calibrated dial.