The state of a mammals' breasts when they enter a cold room or become sexually aroused. Currently being brought to the forefront by certain bra companies who put special padding in their product to hide this completely normal condition. Their tag line being that women need "complete modesty".
"Gee, what a crime people can see I've got nipples, just like the rest of the mammals on the planet earth! I've gone Nippular, deal with it".