noun

• (clothing) A warm cloth cap worn while sleeping, often with pajamas, being common attire in northern Europe before effective home heating became widespread.
  "Winston wore a nightcap to stave off the cold."
• (by extension, figuratively) Something that a person reads or listens to before bed.
  ""[…] and as a nightcap I happened to pick the copy of Plato […]""
• (US, sports, baseball) The final match of a sporting contest, especially the second game of a baseball doubleheader.
• (historical) A cap drawn over the face of the condemned person before they are hanged.

verb

• (intransitive) To drink an alcoholic beverage shortly before retiring to bed.
  "Even better than breakfast, though, is nightcapping at the Waffle House . Nightcapping happens after the bars close, but before the southern sunrise: the hours when their jukeboxes play “Freebird” on a continual loop, […]"