Top Definition
Not quite an erection, but getting there.
When I saw Milla Jovovich's boobies I got a semi.
by Germ March 15, 2003
13 more definitions
the state of a penis which is not altogether flaccid nor erect. It will often occur at inopportune embarrasing times and will be brought on purposefully by a cunning sexy woman pretending she has no idea what she is doing.
"why are you still friends with some of your ex-boyfriends?"

"I like to keep them healthy and providing the regular semi keeps the circulatory system in check."
by MintyLeila June 18, 2005
the in-between state of a limp dick and a usable hard-on. can be on the way to hard, on the way back from hard, or never allowed to get more than 60% (+/-) hard.
many a young man learn to hide their semi with text books after day-dreaming in class
by the mac al February 28, 2006
The word that comes up on t9 phones when the word "penis" is intended to be typed.
I got a text from Benjy that says, "I put my semis in her butt."
by Danielwritesstuff January 14, 2009
A small boner over something none sexually related. It will be about 50% smaller
100% on a maths test forced him to get a semi
by Ben Ski Don May 03, 2010
Semi's is semi losers... Like semi's and full blown
Now we cross the line from semi's to full blown

I hate those fuckin semi's

by Allan S November 21, 2005
The act of fisting your partner with 18 fingers, being 18 fingers for 18 wheels, generally putting 6 in the front, and 12 in the back, often requiring more than 1 person giving the Semi.
I hooked up with Sammy the other day, and she really wanted to bang, but 2 of my other friends wouldn't stop tagging along where we went, so she took my offer for a good ol' Semi, I hadn't seen her again until the obituaries in the newspaper, she died from being too loose, releasing her organs out of her body.
by xXKokOfJusticeXx June 14, 2013

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