the three periods of the hot season, comprising 初伏 chū​fú, 中伏 zhōng​fú, and 末伏 mò​fú, occurring from mid-July to late August; also used more generally to refer to the entire period from the start of the first period to the end of the last

refers specifically to the last of the three hot periods, 末伏 mò​fú

(literary) an ambush utilizing three separate groups of hidden soldiers