The term 'It'll Knock You Out' is a phrase used to describe the effects of certain drugs. The crossword solutions for this term are ETHER (5 letters), Seconal (7 letters), and OPIATE (6 letters). ETHER is an anesthetic that is used to induce unconsciousness, while Seconal is a brand name for a type of barbiturate sedative. Opiates are a class of drugs derived from the opium poppy plant, which have strong pain-relieving and sedative effects. All three of these drugs can cause a person to become unconscious or 'knocked out'.