look up any word, like the eiffel tower:
 
4.
the name given to some one who has a really bad temper and who loses their cool quite a lot. mostly verval towards others or things but at times can be violent
while using the rfid machine it stops working. so semtex starts shouting at it, headbutting it then runs it over with a barra.
Walks about all night giving people abuse randomly.
On a bad night no 1 is safe.
under no circumstances ask to speak to his brother
by weelianne August 06, 2007
 
1.
Shit that gose boom! A plastic based explosive
Holy shit the semtex blew up
by Dfunk Williams November 02, 2004
 
2.
-noun: a called upon member of your team that has been given the duty of "diving on a hand grenade."

i.e. a wingman that has to stick to the fat/ugly chick (like the sticky explosive from Modern Warfare 2) all night, while your boy is running game.
Justin, SEMTEX!

Ha, Pauly is on semtex duty tonight. He's got to stick on the fat chick.
by bolo1g2 January 24, 2010
 
3.
Definition:
A bitch that sticks to you and never leaves you alone.
Example:
This girl is a straight semtex she text me everyday!
by Hebbs and Pflanz August 10, 2010
 
5.
Cool individual from the Liverpool area who can go off like a box of fireworks when called upon
1.In a bar with a rowdy manc, leaps to his feet and kicks the mancs stones out and saves the day for every one in the pub
by Kidz August 22, 2003