Until someone gives you a definite answer I'll give you my best guess. I think this term refers to the fact that the product will cure better in sunlight. Another example is automotive pin stripe tape, (3M). The adhesive on the tape reacts to UV rays and actually sets with a stronger bond if you leave the taped suface outdoors. I use it a lot on my models, and I always set them in the sun for a few hours to let the tape cure. It stays stuck and I never have a piece come loose. Anyway, that's my best guess.