The term 'plunge into boiling water' can be summarized by the crossword solution 'SCALD, ' which is a five-letter word. Scalding is a cooking technique in which food is submerged in boiling water for a short period of time, usually to soften or cook it. It is also used to kill bacteria and other microorganisms on the surface of food. Scalding is a common method of preparing food in many cultures around the world.