Crasser is the comparative form of crass—more crude, insensitive, or lacking in refinement than something else.
His joke was crasser than anything I'd heard at the office.
Each sequel somehow manages to be crasser than the last.
1. vulgar — coarser, More rough-grained; cruder (More unrefined or vulgar); grosser (More disgusting or revolting); lewder (More sexually suggestive); raunchier · smuttier · bawdier · filthier
2. unrefined — coarser, More rough-grained; cruder (More unrefined or vulgar)
Opposites
REFINEMENT AND ELEGANCEcrasser ≠ classier More elegant, sophisticated; subtler · finer
SENSITIVITY AND TACTcrasser ≠ gentler More softly inclined
SUBTLETY AND NUANCEcrasser ≠ subtler More delicately understated; defter