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!"
by DiceOfDeath April 7, 2005
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.
by Bobby Digital October 27, 2006
Sixty Nine that is interrupted, cancelled, or postponed by a period, also written as 6.9
Man, me and Amy were about to do some wild shit but she pulled a six-point-nine on me.
by TheModernDanielWebster November 30, 2016
A form of analingis that occurs between two partners, in which both partners lick each other's anuses.

basically, it's like 69ing, but with buttonholes-- a double rim job.
My girlfriend was giving me a rim job and wanted one too, so to make it fair, we started Six Eighty-nining.
by woahnow February 14, 2014
Guy 1 : Yooo dude why did you pull a six nine last night?
Guy 2 : I didn't get laid..?
Guy 1 : Oh no of course not! why did you snitch on us at the party last night
Guy 2 : yo i gotta go all the sudden man
Guy 1 : wait dude tell me!
Guy 2 : Nah im out bitch
by sub to Bombastic Lists May 1, 2020
To get told on or thrown under the bus in order to safe face.
Rachel six nined her sister so that she would not get into trouble.
by Captblack85 September 28, 2019
six nine is going to jail for 50 years #sixnine #treyway
by MoreMoneyMoreLife November 29, 2018