used to refer to quick robbery by an aborigine in australia. usually in queensland.
'who robbed the house bruce?' "Dunno Sheila I was on the dunny but I saw a brown flash'
by tadge72 April 24, 2010
In the oscillations between struggling not to shit and feeling perfectly fine (somewhat analogous to contractions during child birth), the brown flash is the temporary but dire need to take a shit. Often results in sweating, heavy breathing, and a clenching shut of the asshole to prevent shitflow.
After 2 hours of holding in a shit I was brown flashing incredibly hard. My feelings of intense need to shit were becoming closer and closer together and I knew if I did not shit soon I would ruin a pair of innocent underwear.
by IShitALot September 14, 2014