To tease is to pick on someone or to give false hope. You can tease your little sister by saying "nanny nanny boo boo" or by holding a cookie just out of her reach.
Tease, a modern spelling of the Old English taesan “pluck, pull apart" is now associated with the act of harassing. You can still use tease as a verb, though, to describe the act of backcombing your hair to give it volume. But more commonly, tease refers to messing with someone. There’s an old proverb, “Patience when teased is often transformed into rage,” which means if you tease someone a lot, you might get your booty kicked!