The crossword solution for the term 'IT WILL KNOCK YOU OUT' is 'OPIATE', which is a six-letter word. An OPIATE is a drug derived from opium, which is a naturally occurring substance found in the opium poppy plant. Opiates are used to treat pain and can have a sedative effect, leading to feelings of relaxation and euphoria. However, they can also be highly addictive and can lead to serious health problems if abused.