A niner is not just what you call freshman at high school it can also be anyone at any age. Anybody who messes something up in their life is considered a niner.
Mclellan: I just lost all the money that I invested in this company

Mr Chittle: You stupid niner
by The Chocolate Leopard April 11, 2010
Niner is a rite of passage ceremony marking entrance or acceptance into a group or society in High School, required for grade nine students to be fully "accepted" into the student community.
Another word that could be used for this term is Initiation. However niner is a more specific term referring only to grade nine initiations.
This type of initiation is mostly done in school trips that require students to sleep over,(for example; Muskoka Woods camp) and at night around 1:00 to 3:00 AM, grade 11 or 12 students would wake up, and go around "initating" niners in their sleep.
This term is a new type of initation, started in Bishop Allen Catholic High School, in Toronto, Ontario, Canada.
The following could be considered ninering, having your hair sprayed into a vivid color, usually green, having shaving cream sprayed on your face, or make you do ridiculous things (if not in a school trip.)
by Gman_0000 September 12, 2007
Trucker talk used on CB radios to make the number 9 sound cool when relaying directions, coordinates or instructions. Also used in the military. You have to be an uptight angry white male with either a buzz cut, aviator sunglasses or a flannel shirt to use this term.
"We've located Charlie at DELTA, BRAVO, point NINER, over."

"The $2.99 omlette and vanilla shake deal is at the Oasis off of I-two-oh-niner, little buddy. For another 2 bucks the waitress with show you her tankers."
by chulo4mami October 9, 2009
an erect nipple stimulated from sexual arousal, cold weather, etc. Thus, "niner" is a slang term for the combination of the words "nipping" and "boner."
It's so cold that I got an instant niner when I walked outside!
by kbl October 11, 2017
a nine-inch penis, any abnormally large penis
She got stuffed with a plump niner
by Mrs. Jenkins July 14, 2008
No, nope
Comes from the german word for no (nine)
nine can also be used in the place of niner
At first was used mainly by scros, but now almost everyone uses it.

also
Scro 1: I heard she gave you a beeje after the lax game
Scro 2: Shob, Niner, i wish!

Person 1: hey do you have the latin homework?
Person 2: niner

Person 1: duuuuuuuuuude she is so HOT
Person 2: NIIIIIIIIIIIIIIINNNNNNNNNEEEEEEEE
by falalalalallaaaaaaaaaa April 21, 2011
To look gay, stupid, weird. But more along the lines of looking like a gay, stupid, or weird german or jew.
"Wow look at that faggot, i hear he just moved here from germany. What a Niner!"
by mynameisshepimpsavage August 3, 2009