When someone's had a lot of
modifications made to their
penis, oftentimes it results in sundry
effects on the
urine stream. A sprinkler-head effect is when the urine comes out like, well, a
sprinkler - either one of those
flat ones which makes a nice
rainbow arc back and forth across the lawn, or a
round one which sprays out in all
directions.
On a similar note, a female-to-male transsexual may encounter a problem with his new penis: the skin used isn't used to standing up to urea, and it slowly gets dissolved by their own urine. End result? This. (Though in this context it's usually referred to as a shower head, rather than a sprinkler head, probably because it's much more like a shower than a sprinkler.)