bird's nest
noun
1
pubic hair that can be seen to extend from the crotch to the navel; pubic hair. Homosexual use; tangled imagery US, 1972.
2
in the Royal Navy, a WRNS' cabin. A member of the Women's Royal Naval Service is popularly known as a Wren, hence this pun; remembered from World War 2 but not recorded until 1984 UK, 1984.
3
the chest, especially (of a man) if hairy. Rhyming slang, but also partly from the imagery. UK, 1970.
4
a hole in the upholstery of the driver's seat of a car from long use and too much weight US, 1992