Painful redness and inflammation of the skin caused by too much exposure to the sun's ultraviolet rays.
Simple compound of 'sun' plus 'burn,' dating to the 1500s when English speakers began describing the sensation of overexposure to sunlight as analogous to actual burning.
Before widespread sunscreen, sunburn was just called 'getting the sun'—the word 'sunburn' only became common when people realized UV damage was actually a chemical burn at the cellular level!
Complete word intelligence in one call. Free tier — 50 lookups/day.