The leggings illusions is when a girl with no ass wears super tight leggings to make it seem as if she has ass when she doesn't. This makes the ass look big from a distance, and makes a man's mouth drool for dat booty. But when you get close or you get her home and taking them legging off, you realize that she has a small ass.
It's still sexy, but it's a lie.
Britney was so fine, she had a nice ass when I saw her walking around campus. Then I got her in my dorm, she took off the leggings, and I realize that she had a small ass.
When one loses control of his or her legs while running at high speeds and they flail about uncontrollably till the person falls or regains control of their legs.
Commonly occurs while running down hill or while running on uneven terrain.