E-mailing while inebriated.
I downed a half pint of scotch and spent the rest of the night derailing old girlfriends.
by Folook November 27, 2007
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DERAIL; a term used by the shmoo clan in order to replace shit, do it, and pwn.
1) Dude i have been holding this in but i really gotta deRail!!
2) Are you ready? Lets deRail!!
3) Dude you just got DERAILED!
by Nathan C. August 26, 2005
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Attacking or failing to follow the tactics of a debater who railroads the conversation, by expressing unexpected views or challenging logical fallacies.
She's upset because I took a third option that will derail her planned one-sided conversation.
by Poor Lurker August 2, 2012
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1. During the act of doggy-style vaginal intercourse, the male, while recovering from a thrust, pulls out too far and his penis "accidentally" inserts itself into the girls anus.

2. An arctic map in the video game "Call Of Duty: Modern Warfare 2."
1.

"The other night my girl moaned some other guys name, so I derailed her. See if she does that again..."

2.

"Last night I was having some fun, then got derailed"
"You pulled out too far and got mud on your junk?"
"Worse. I got that shitty snow map."
by FunkyPunkyJunky March 20, 2010
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To move from the pink, to the brown, when making the sweet sweet sechzor.

Or if you'd like it a bit clearer:

To go from vaginal to anal intercourse
Man A: Dude, I tried something new with my girl last night.
Man B: Oh yeah, what's that then?
Man A: Well, I went from pink to brown.
Man B: Oh...you derailed!! Fair play matey.
by Sid P June 13, 2007
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When you are railing your rib, cleopatra, bottom bitch, and wife of 14 years. And you slip into the wrong hole. This is called a derailment, and doesn't matter what hole.
Jim: fuck this feels good
Susan: oooooohhh ya harder harder
Jim: (slips into wrong hole)
Susan: ooooaaaahhhhhhhh

Jim: sorry babe I derailed
Susan: ok, next time I dont cause a derailment into me
by Cochieman 456 November 27, 2020
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A women losing her virginity in a very rough, hard manor.
Guy 1:Dude, I totally just derailed this one chick!
Guy 2: Me too!
by Wendy (bob's girlfriend) October 12, 2008
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