nightcap

Short definition from Wiktionary

Noun

1. 1
   A warm cloth cap worn while sleeping, often with pajamas, being common attire in northern Europe before effective home heating became widespread.
2. 2
   A beverage drunk before bed that is usually alcoholic.
3. 3
   Something that a person reads or listens to before bed.
4. 4
   The final match of a sporting contest, especially the second game of a baseball doubleheader.
5. 5
   A cap drawn over the face of the condemned person before they are hanged.

Verb

1. 1
   To drink an alcoholic beverage shortly before retiring to bed.