rampant

Short definition from Wiktionary

Adjective

1. 1
   Rearing on both hind legs with the forelegs extended.
2. 2
   Rearing up, especially on its hind leg(s), with a foreleg raised and in profile.
3. 3
   Tilted, said of an arch with one side higher than the other, or a vault whose two abutments are located on an inclined plane.
4. 4
   Unrestrained or unchecked, usually in a negative manner.
5. 5
   Rife, or occurring widely, frequently or menacingly.

Adverb

1. 1
   Rampantly.