The only differences (bar some very obscure words) between US and UK (ugh! , include Ireland in that) is the letter 'u' for such words as colour/color arbour/arbour and the 'shun' words such as connection/connexion. 'Bumming around' is aterm used this side of the pond (as is 'bum' for someone who does little with their life) but 'bum' does predominantly stand for a posterior/derriere/behind/backside/lower back. No wonder we want to shorten it!!