RUL: Acronym for the right upper lobe (of the lung). The right lung has three lobes: the right lower lobe (RLL), the right middle lobe (RML), and the right upper lobe (RUL). The left lung has but two lobes: the left upper lobe (LUL) and the left lower lobe (LLL). The reason why the right lung has three lobes whereas the left lung has only two is no... Found on http://www.medterms.com/script/main/art.asp?articlekey=7181