From Longman Dictionary of Contemporary Englishnightcapnight‧cap /ˈnaɪtkæp/ noun [countable] 1 DFDDRINKan alcoholic drink that you have at the end of the evening, just before you go to bed2 DCCa soft hat that people used to wear in bed
Examples from the Corpus
nightcap• Well, Trippy said he slept better after a nightcap.• As the party was breaking up, Joe quietly invited young Franklin and Harry Hopkins home for a nightcap.• Afterward, Mr Dent walks him home, shares a nightcap and makes a pathetic attempt at seduction.• Then he slipped under the bedcovers dressed in her gown and nightcap.• In the last cliffhanger, downstairs lover Tony Head was caught sharing his Gold Blend nightcap with a mystery lady.• I had suggested that some of our guests might enjoy a post-wedding, post-reception, post-dinner nightcap in our hotel room.• It was time for my nightcap.• One had a kind of bunched white nightcap, in white dimity edged with lace. 