What are the definition of these triangles?

I’ve been seeing a lot of these triangles lately and I was wondering what it was meant?

Here’s a picture of the triangles: http://23.media.tumblr.com/tumblr_kr3yzoPRa81qzxqito1_500.jpg

I’ve noticed that a guy had tattooed some of these triangles on his arms and he said it has to do with the band Owl City but I think it’s more than that.

P.S I know these triangles means Delta but I’m looking for another definition of it.