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1.
Short for no reply, when two lads are texting one another before bedtime and to avoid all of the good night followed by another good night bullshit, one of the lads simply sends "no rep" to inform the other lad that said lad is going to sleep and that the second lad should not reply to his text. It is commonly used to prevent the annoyance of continous vibrations of the phone once a lad has decided to get some sleep.
Lad 1-"Yeah man that chick was mad hot"

Lad 2-"Defo man, finest piece of ass ive ever seen but I'm gonna cut to bed now mate so ill c u tomoro, no rep."

Lad 1-" "
by I.C.E December 20, 2011
 
2.
'No rep' is the term used in Crossfit when a person fails to sufficiently complete a movement according to the rules.
My scorer kept 'no repping' me even though I'm pretty sure I was getting low enough on the overhead squats.

The new coach at our gym is the 'no rep' king.
by cstrap May 24, 2014