Rampant is a word used in heraldry, the system of rules used to construct coats of arms. When a lion appears on a flag or a shield, it can be in many different positions or 'attitudes' - lying down, walking, sleeping etc. A lion rampant is standing up on its hind (back) legs with its mouth wide open to make a loud roar, and its paws raised to strike. See https://en.m.wikipedia.org/wiki/Lion_(heraldry) for pictures and names of this and the other attitudes.

I think it is hind leg not hint leg. hind leg means the back limb of an animal.

Thank you very much, this sentence is for like a rampant lion or a rampant dog. That's interesting, I won't never forget it!!!

"hind legs" means back legs. For example: "a bear standing on its hind legs" means a bear standing on its two back legs. "roaring" means for an animal to let out a loud shout or cry; the sound a lion makes when it shouts. for example: "the lion roared"