129th Base 

Having sex and not having sex at the exact same time.

Tom: wait, how do you even get to 129th base?
Bill: the easiest way is to fuck Schrödinger's Cat

129th Base by mmm.grapes December 26, 2009

169th Base 

To have sexual intercourse with a monkey (any type of monkey) while having Cheese inserted into your arse.

Guy 1 : Hey, i got to 169th base last night.

Guy 2 : Remember the cheese?

Guy 3 : Hell yeah, i used Bree.

169th Base by IcyDeigh March 25, 2010

19th base

having sex with an inanimate object yet still reaching an orgasm. the object must also orgasm.

only 2 people are known to have achieved this. ron jeremy and chuck norris

ron jeremy: i got to 19th base with that sexy tree down the road

chuck norris: *ROUNDHOUSE KICK*

19th base by andrew osullivan September 11, 2006

12th base 

To defy the laws of physics whilst engaging in sexual intercourse.
A common example is to have sex listed as the 'Bat Position' in the karma sutra, and that is to have sexual intercourse on the ceiling.

I went to 12th base last night and i got such a rush to my head.

12th base by Rhodri Griffiths July 30, 2008

12th base 

A sexual act including a saddle and/or table tennis paddle

guy 1: we got so far last night
guy 2: what base
guy 1: 12th base
guy 2: Woah!!! how did u get a saddle into her car

12th base by Super Robo Boogie Bot II October 10, 2008

12th base 

When your girlfriend removes her glass eye and you prodceed to insert your penis inside the hole and fuck her.

Guy 1: "Dude we got to 12th base I don't deserve to live anymore."
Guy 2: "shit bro I'll get my bat."

12th base by Shaniquaobamaniqua September 17, 2013

149th base 

Sit there listening to opera, whilst eating a biscuit making sexual noises

'Dude! I totally did 149th base last night!'
'Gees dude, that's grose'

149th base by lalalalalalaaaaa January 18, 2009