To make sour; to cause to become sour or acidic.
From 'be-' (causative prefix) plus 'sour' (Old English 'sūr,' from Proto-Germanic *sūraz, meaning sour or bitter). The 'be-' prefix makes it transitive.
The verb 'besour' shows how English once had verbs for simple actions we now express differently—modern English would say 'make sour,' but 'besour' is more elegant and direct!
Complete word intelligence in one call. Free tier — 50 lookups/day.