a mash-up is slang for a get together of similarly minded people so that they might partake in the consumption of drugs and/or alcohol. people on a mash-up get mashed.
mash-ups usually take place at night, but usually go on well in to the morning of the following day (they tend to wind down when the alcohol/drugs run out). unlike a cotch, mash-ups can take place anywhere, in or outside.
H: YOOOOO MAAAAAAAAAAAAAAAAN, on for a phat mash-up tonight?

M: YEAAAAAAAH BLID, let me ring fattypants whitworth and the filthy pikey, see what they's sayin'

H: bring some shroooms blud

M: wouldn't be a mash-up without them
by mr 9" September 3, 2007
Get the mash-up mug.
(of a DJ) to play a set that excites the crowd
That was mash up me bredrin!
by piffy June 12, 2003
Get the mash up mug.
To make a hot drink
your going to ''mash up''
''I'm going to mash up, do you want a coffee''
by Twitchyxx8 July 23, 2009
Get the mash up mug.
Getting drunk, then high, then awesomely stupid for a period of indeterminable length, but generally must last at least an evening plus all night and some of the morning. Mash-up heads will take anything to increase the length of time to talk nonsense. Evening ends with possible bed wetting episode or discussion about love/drugs/energy/music. Pizza is often ordered the next day.
-Me gonna get mmmmmmmmmmmash-up.

-"Is that Tom over there fucking up his mixes, he sure is a shit deejay."
"Cut him some slack, he is mash-up."

-Look, its my day off tomorrow and I wanna get totally mash-up.

-"Mash up, get me crack up, on the rack up, shut up and smack up, on a track up" Apocryphal song attributed to someone who is mash-up creating a new and awesome track.

-You look mash-up.

-Mum, I got fuckin mash up last night.
by Sunrise Soup May 15, 2010
Get the Mash-up mug.
He was completely mashed up.
by Alastair November 19, 2003
Get the mashed up mug.
A sexual act involving three people whereby a man has intercourse with a women assuming the doggie-style position and a third person (man or women) inserts their hand into the bottom of the women and gives the man a hand-job from the inside.
-how'd you go last night buddy?
-awesome. Got myself a Milwaukee Mash-up after dinner.

-about time!
by Wong Poker September 26, 2017
Get the Milwaukee Mash-up mug.
When the music paying from two cars sounds like one song.
While driving and listening to house music, the rap lyrics in the car next to me made a perfect traffic mash-up.
by sojaigirl May 1, 2013
Get the traffic mash-up mug.