“You're such a tease!”

Your birthday is in one week. Your girlfriend bought you a gift. She shows you the box and asks if you want to know what it is, but won't let you see it. You say:

You're such a tease!

(someone) is such a (something)

The word "such" is similar to "so" except it's used with nouns instead of adjectives:

He's so handsome.

I used to be so lazy.

You're so goofy.

He's such a good-looking man.

I used to be such a procrastinator!

You're such a goofball!

(someone) is a tease

"A tease" is a person who plays with other people's desires. They offer something that you want, but then don't give it to you.

For example, "a tease" very often describes a woman who acts like she's attracted to a man, but then won't go out with him or sleep with him.

Despite its meaning, the word "tease" doesn't really sound very negative. It sounds kind of fun and playful.