Billows

[Justin Bieber]

The quality of having or being billowy, cloud-like, fluffy, or otherwise over-flowing. Often used to refer to ladies with big, squishy natural breasts that you wanna sink your face into

[Merna]

Boobs that can be used as pillows

[Jessica]

to spread over a large area, or (especially of things made of cloth) to become filled with air and appear to be larger: