look up any word, like cleveland steamer:
 
1.
The effects are similar to jet lag, but on this occasion the overwhelming tiredness is owing to a night full of bollock-draining sex. the following day they can't function properly in every sense of the word.
-Fancy coming with us for a kick about this morning?
-Fraid I can't, mate. I just don't have the energy.
-Suffering from Shag lag, eh?... Lucky bugger.
by Bottom Face March 17, 2011
 
2.
When your watching porn on the internet and your connection is slow so your porn is jumpy and the sound is off beat with the action.
"man i was having a bat last night till i hit shag lag and i didnt know if i should keep going or stop"
by Cheyne Grainger June 13, 2007
 
3.
Fatigue following a rollicking sexual encounter.
Woman: Ready for another turn in the sack, honey?
Man: Would ya bleedin' leave me alone, I've terrible shag-lag after that!