To describe a noun or pronoun that is as awesome as cats, which are clearly very awesome indeed.
Typically used to express one's appreciation after having witnessed an impressive display of skill, or to impress upon others the level of one's own skill.
Especially applicable to anything which involves a high degree of dexterity, mental focus and cat-like reflexes.
"Shit yeah, I just got a 25 kill streak in Call of Duty! I'm wicked catsome!"