What do yo mean by "rule out pneumonia" in my report? does this mean i have something other than pneumonia

Depends: "rule out pneumonia" can be phrase clinician places on radiograph request if certain physical findings and fever are present. If findings of consolidation are seen on chest radiograph sometimes it can represent volume loss or pneumonitis. Sometimes findings are not specfic and radiologist can suggest compare with clinical findings to "rule out pneumonia".

Rule out pneumo: I'm not sure what your report specifically said, but "rule out" any diagnosis means that this possibility needs to be investigated clinically to see whether your condition shows other signs of it. There could be multiple explanations for your symptoms or diagnostic test results --so they're telling the doctor to do further exams, etc that can "rule out" (or rule in) pneumonia.

Most likely dx.: It generally means you may, or most likely have pneumonia based on ( presumably )x-ray appearance particularly if it fits with history. It does not guarantee pneumonia, however, particularly if it does not fit the clinical picture( the history, exam).