DJ's sometimes play long sets. I put on long mix, line up the next tune and make a dash for the urinal. A 'Slash Dash'.
It could be used in other situations where there is a short time for the toilet visit: a break in a long meeting, between tasks on a timescale project like filming, between cue's in a show.
Used most commonly by European males as a threat. Usually involves some form of violence involving a knife or sharp object, and proceeding to run from the scene of the crime.
If you come near me again bro, I will slash you dash you.