To make or become coarse or rough; to reduce in fineness or refinement.
From coarse + -en (verb-forming suffix), similar to how darken comes from dark. The verb form emerged in English to describe the process of becoming rough.
Skin coarsens with sun exposure, fabrics coarsen with washing, and voices coarsen with age—it's one of nature's ways of showing wear and time.
Complete word intelligence in one call. Free tier — 50 lookups/day.