A few throw up-s I've spotted around Leeds so far, A throw up is a quick Fill colour with an outline that takes less than 10 minutes. Heres a quick definition off urbandictionary;
A throw up is a quick graffiti bomb. Usually not
the writer's full name. An Unfilled throwie is a hollow. If a throwie
is filled its usually a crack-fill(quick back and forth strokes with
fill colour).