What is x?
x is ,X (noun) 1. the twenty-fourth letter of the alphabet, between W and Y 2. used to in- dicate an unknown person Let’s take the example of Mrs X, who is a widowed lady 40 years old. 3. a mark like a cross, especially on a map To find the treasure, you have to find the spot marked ‘X’ on the map. 4. an unknown mathematical value symbol 1. a multiplication sign 3 x 3 = 9. (NOTE: say ‘three times three equals nine’) 2. showing size The table top is 24 x 36cm. (NOTE: say ‘twenty-four by thirty-six centimetres’)
source: Easier English, Student Dictionary Upper Intermediate Level