There is several meanings, the most prominent one being that it is a symbol of Thor, of untamed natural force, lightning and such. It is also believed to deal with the 4 seasons, cycles of nature and similar.
I'm in absolute awe. I'm female, and I even wish I could get a sleeve done like this. I've enjoyed body modification since I was very young, I have images and picture of myself touching my uncle's sleeves. But this. This is put me into real love, and appreciation, for artists like yourself. One word: Wow. We need more artists like you around here.