base 13 

A nonstandard numeral system That uses the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, X, E and T. and so 10 would equal 13 in this numeral system.

What do you get if you multiply six by nine? forty-two.

base 13 by Adeadlyliquid October 18, 2004

13th Base 

having sexual intercourese with your partner while wearing Sherlock Holmes hats, smoking pipes and completing a crossword in under 10 minutes.

I got to 13th Base with the wife yesterday and she came allover my deer stalker

13th Base by sergio97 January 1, 2011

13th base 

Sex with your boss, professor, or another person you have no business fooling around with . . .

"I did not have sexual relations with that woman . . . it was just 13th base!" -- Bill Clinton

13th base by Scylla June 29, 2006

13th Base 

When you have sex with an animal and a person at the same time.

"Dude, that weird dude next door got to 13th base last night."

13th Base by Mr. Supotco November 13, 2015

13th base 

(male) when you have intercourse with a female and you end up getting warts, aids, and every other STd you can think of.

Man this girl took me to 13th base and now my life is over!

13th base by Will Deshazo June 11, 2006