The word "humper" has a few different meanings and can be used in different contexts. One meaning of "humper" is a person or animal who carries heavy loads on their back. Synonyms for this could be a porter, a pack animal, or a mule. Another meaning of "humper" is a bump or protrusion, such as a speed bump on a road. Synonyms for this could be a hump, a bump, or a ramp. Finally, "humper" can also be used as a slang term for someone who is in a bad mood. Synonyms for this could include grump, grouch, or sourpuss. Overall, the word "humper" is versatile in its meanings and could have various synonyms depending on the context.