Noun - A Unit of Time = 1 hour in a 40 hour work week (ie. 1/40)
You begin work at 8am on a Monday morning. At 9am a co-worker looks ("prairie-dogs") over the cubicle wall and suggests getting a cup of coffee. The co-worker then states "How's it going?" and you reply "Great. Only 39/40ths until the week is over."

by Lawrence Nelson February 24, 2006
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Two trains on the same track are moving towards each other, each at a speed of 40 miles per hour. On the top of one train stand 50 naked guys with boners. On the other train stand 50 naked girls who are horny. What happens to the ones that don't fall off when the two trains run into each other is called 40th base.
Damn, i just got an orgasm from 40th sure was pleasureful...
by gretaaaaaaaaaa July 27, 2008
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Odd One Out. As people usually goes out with at least 3 peoples, so the multiples of 3 to 39, 40th wheel.
"OMG! please come to the club, I'm the 40th wheel!! = "
by Harmarkev October 1, 2011
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The last of all bases. To turn yourself into a transexual and then rape your best friend and mother.
A- Sorry about your asshole I just wanted to get to 40th base.

B- I understand.
by ALo╛Prezidente July 17, 2008
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having your roommate walk in while jacking off to a picture of his mom, and then joining....similtaniously sticking a frozen banana up a monkeys twat.
guy one: dude awesomest thing happened last night!!!!!!
guy two: what?!
guy one: i got some serious monkey action.
guy two: no way! 40th base?!?!? well done dude!

by dangletsbang August 2, 2008
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making out with somebody's 2cm flesh tunnel.
dan - duuuuuuuuude i just got to 40th base with ginny.
random stranger - you mean you kissed her 2cm stretched ear! aweeeeesome!
by gintingz July 28, 2008
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When you're nearing the end of your work week, still on the clock, and you spend your last precious moments productively seated on a toilet letting your excretory system gets some exercise. A foolproof method to greeting the weekend, now that you've made your money and gone on one final business trip to the bathroom.
"We all begrudgingly attended the 4pm meeting on Friday, that is except for Jared. He had to meet with the toilet for a 40th hour dump."
by Cloudkicker April 17, 2015
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