三长两短

unexpected misfortune / unexpected accident / sudden death

three / 3

length / long / forever / always / constantly

chief / head / elder / to grow / to develop / to increase / to enhance

two / both / some / a few / tael, unit of weight equal to 50 grams (modern) or 1⁄16 of a catty 斤[jin1] (old)

short / brief / to lack / weak point / fault