More of a sniglett, but is very commonly known as the black streak build-up of wet road debris (mostly dirt & who knows what else) that collects on the back of your shirt or coat as you ride a bicycle in the rain.
My jacket was streaked in backspacle from the water coming off of my back bicycle tire after riding in the rain for hours.
1. (verb) The act of ejaculating onto the fifth lumbar spine vertebrae area (part of the greater lumbar region) of a woman's back. To the human eye, this region is the curve just above the buttocks, which is also commonly referred to as the small of the back.
2.) (noun) The residue of male ejaculatory fluid after it has been deposited onto the lower back.
"I wouldn't want todate her, but I'd backspackle her."
When you are tripping on your own thoughts. Can be pleasant or unpleasant, and can be the birthplace of both amazing and terrible ideas.
You have to experience it to be able to know what it truly is.