x--Sister Jen's Birthday word

x ¹ or X  (ks)

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 or X'd, x'ing or X'ing, x's 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.

Context
According to Roy Blount Jr. in his book Alphabetter Juice (which Sister Mary gave Sister Jen for Xmas), "x" is the shortest verb in the English language; the baseball word k and the work t, as in "teed off" are both generally used in the past tense.