A play on the phrase "no one", where "one" is replaced with "pony". It is used by the characters in my Little Pony and is also commonly used by bronies.
adj.
1) cute, adorable, lovable, cuddly.
Generally conveying the sort of maternal emotion that a mother would feel towards a baby, and primarily used by teenage girls to refer to something small and baby-like to which they feel affection.
interj.
2) Said (or "squealed" is a more accurate word) when the speaker feels the affection described by noony(1) and wants to vocalise this affection. Once again, primarily used by teenage girls.
basically the pubes on a noony, noony meaning vag. Can also mean when the treasure trail is connected to the rest of the pubes. Basically just a whole lot o' pubes everywhere can be called a noonybrow, as long as they're found on de poosay.
Jim: my girlfriend is startin to piss me off.
Paul: why is that Jim?
Jim: Well paul, she just refuses to shave off her noonybrow, she won't even trim the damn thing.