Definition from Wiktionary, the free dictionary
nightcap (plural nightcaps)
- A warm cloth cap worn while sleeping, often with pajamas, being common attire in northern Europe before effective home heating became widespread. [From 14th c.]
- Winston wore a nightcap to stave off the cold.
- A beverage drunk before bed that is usually alcoholic. [From 1818.]
- I'll make myself a nightcap of whisky and lemon before heading to bed.
- (by extension, figuratively) Something the person reads or listens to before bed.
- (US, sports, baseball) The final match of a sporting contest, especially the second game of a baseball doubleheader. [From 1939.]
warm cap worn at night