Jrock is the short version for "Japanese rock", which includes Visual Kei, normal and alternative rock, but from Japanese bands. The term sometimes includes Japanese metal bands (such as Maximum the Hormone), but it's more rarely seen.
The most popular Jrock band in Japan is SID, but the GazettE has a lot of fans outside the country. They play Visual Kei and DOES plays normal rock in Japanese.
When you have to pee in a movie but don’t want to miss anything, and must do the following mental equation: will the amount I have to pee cause enough discomfort to diminish my attention capacity for the remainder of the movie to an extent which is greater than the amount of the movie I would miss by making a mad dash to the restroom.
I saw Satantango last night, wonderful film but by the 5th hour I had to start doing pee calculus.