six by nine 

1) Car stereo speakers producing massive amounts of treble and ear-splitting assloads of mid-range noise, while putting out very little bass. Sound great with larger speakers to back them up, but popular even when no such speakers were available for automotive use (this is one of the enduring mysteries of our time).
2) The answer to life, the universe, and everything, as imagined by Douglas Adams in "The Hitchhiker's Guide to the Galaxy" (6 x 9 = 42 in base 13).

"Dude! Those new six by nine's you got are totally tweakin' my eardrums!"

six by nine by DiceOfDeath April 6, 2005

six by nines 

A large areola or "nipple" when referring to a woman's breasts; or a woman with large areolas or nipples. May refer to areolas that are oblong in shape.

She had nice tits, but when she took her shirt off she had straight six by nines.

six by nines by Bobby Digital October 27, 2006