an amorphous undelineated mass of tit, often caused by old age sagginess or bras that squish them together. in theory, it could be a single cycloptic tit.

Condition when a woman wears a tight lycra fitted tube top for exercising and looses form of two boobs to just one

When it looks like you have one massive breast. This usally happens when a girl wears a sports bra or one of those tank tops with the shelf bra.

When a woman's bra isn't very supportive and doesn't separate, squeezing the boobs together, thus forming the appearance of one large boob. This usually happens with sports bras.

A case of the rare condition called symmastia, in which a woman's two breasts literally grow together and join in the middle of the chest, so it looks like a single dumbell-shaped breast across the chest. It can be a congenital condition or a complication arising from breast augmentation surgery.

Noun.

1. In art, a singular curve/line/lump of breast used to represent two boobs under clothing.

2. A single mass/breast where two should be, but not where two were originally (if you loose one boob, its not technically a uniboob). A uniboob is the presence of an original single boob.

When a larger chested woman wears a sports bra it is tremendously restricting. It is described as -- A large lump of two breasts squeezed together by the wearing of a sports bra. The end result is that the woman's breasts no longer have the "Lift and Separate" affect. Therefore causing the appearance of "One Boob".