<interjection> Chiefly Anglo-Scottish Slang;
Used to express a sexual attraction to another person.
--> The term is abnormal; There is no definite rule to using the word. Although, being an interjection, a rule of thumb would be to use it in the same way as "Wow
." It is kind of the same as saying, "Hey, I want to shag
you!" only in a single word.
As with most slang, the only way you can use it is how you feel it should be used...