Take a look at the weld profile example sketches. Most ugly welds have unacceptable profile - usually overlap and excessive reinforcement. Grounds for rejection.
Keep in mind that the definition of a 'Gorilla weld' is big, fat, ugly and strong. Very few ugly welds are weak; however most ugly welds fail to meet D1.1 profile requirements. And maybe 1/4th of the welders producing ugly stuff will fail an on-demand welding test. If you are the Inspector-of-Record, CWI or not, you have the right to demand that a welder retest "right now, right here" if his/her work is suspect. Not proven to be all bad, just reasonably suspect.