X (x)

1 plural X's,x's noun (C)

1 the 24th letter of the English alphabet

2 the number 10 in the system of roman numerals

3 technical a letter used in mathematics to represent an unknown quantity or value: if 3x=6, x=2

4 a mark used to show that a written answer is wrong

5 a mark used to show that you have chosen something on an official piece of paper, for example when voting

6 a mark used instead of a signature by someone who cannot write

7 a mark used to show a kiss, especially at the end of a letter

8 a letter used to show that a film is not suitable for people under 18

9 a letter used instead of someone or something's real name because you want to keep it secret or you do not know it: At the trial, Ms X said that she had known the defendant for three years.

10 X number of used to say that there are a certain number of people or things when the exact number is not important

11 X marks the spot used on maps in adventure stories to show that something is buried in a particular place

2 verb X out sth phrasal verb (T) AmE to mark or remove a mistake in a piece of writing using an X cross out cross 1