Rampant

[ram-puh nt] /ˈræm pənt/

adjective
1.
violent in action or spirit; raging; furious:
a rampant leopard.
2.
growing luxuriantly, as weeds.
3.
in full sway; prevailing or unchecked:
a rampant rumor.
4.
(of an animal) standing on the hind legs; .
5.
Heraldry. (of a beast used as a charge) represented in profile facing the dexter side, with the body upraised and resting on the left hind leg, the tail and other legs elevated, the right foreleg highest, and the head in profile unless otherwise specified:
a lion rampant.
6.
Architecture. (of an arch or vault) springing at one side from one level of support and resting at the other on a higher level.
/ˈræmpənt/
adjective
1.
unrestrained or violent in behaviour, desire, opinions, etc
2.
growing or developing unchecked
3.
(postpositive) (heraldry) (of a beast) standing on the hind legs, the right foreleg raised above the left
4.
(of an arch) having one abutment higher than the other
adj.

late 14c., “standing on the hind legs” (as a heraldic lion often does), thus, also, “fierce, ravenous” (late 14c.), from Old French rampant, present participle of ramper “to climb, scale, mount” (see rampage (v.)). Sense of “growing without check” (in running rampant), first recorded 1610s, probably is via the notion of “fierce disposition” or else preserves the older French sense.