This is an exert from The Original Australians by A. A. Abbie published by London, Muller 1969:
It is the term used to describe penile subincision, the process of urethrotomy, where the bottom of the penis is cut and the urethra is slit open, from the urethral opening to the base. The slit length can vary.
This is an old Australian tradition that used to be referred to as Mika or the Terrible Rite.