• (RP) IPA: /ˈnaɪt aʊl/
• (GA) IPA: /ˈnaɪt ˌaʊl/

night owl (plural night owls)

1. An owl (order#Noun|order Strigiformes) that is nocturnal.
   • c. 1591–1592, William Shakespeare, “The Third Part of Henry the Sixt, […]”, in Mr. William Shakespeares Comedies, Histories, & Tragedies: Published According to the True Originall Copies (First Folio), London: Printed by Isaac Iaggard, and Ed[ward] Blount, published 1623, OCLC 606515358 ↗, [Act II, scene i], page 153 ↗, column 1:

     Their Weapons like to Lightning, came and went: / Our Souldiers like the Night-Owles lazie flight, / Or like a lazie Threſher with a Flaile, / Fell gently downe, as if they ſtrucke their Friends.

   • 1595 December 9 (first known performance)​, [William Shakespeare], The Tragedie of King Richard the Second. […] (First Quarto), London: Printed by Valentine Simmes for Androw Wise, […], published 1597, OCLC 213833262 ↗, [Act III, scene iii] ↗:

     For nightowles ſhreeke where mounting larkes ſhould ſing.

   • 1832, Jedadiah Cleishbotham [pseudonym; Walter Scott], chapter VIII, in Tales of My Landlord, Fourth and Last Series. [...] In Four Volumes, volume IV (Castle Dangerous), Edinburgh: Printed [by Ballantyne and Company] for Robert Cadell; London: Whittaker and Co., OCLC 81177709 ↗, page 220 ↗:

     The well imitated cry of the night-owl, too frequent a guest in the wilderness that its call should be a subject of surprise, seemed to be a signal generally understood among them; [...]

   • 1892, Walt Whitman, “O Magnet-South”, in Leaves of Grass […], Philadelphia, Pa.: David McKay, publisher, […], OCLC 1514723 ↗, page 360 ↗:

     O the strange fascination of these half-known half-impassable swamps, infested by reptiles, resounding with the bellow of the alligator, the sad noises of the night-owl and the wild-cat, and the whirr of the rattlesnake, [...]

2. (idiomatic) One who goes to bed#Noun|bed late, or stays up late at night or in the early hours of the morning.

   Synonyms: nighthawk, night person

   Antonyms: day lark, early bird, lark, morning person

   • 1904 May, Winston Churchill, “Louisville Celebrates”, in The Crossing, New York, N.Y.: The Macmillan Company; London: Macmillan & Co., Ltd., OCLC 9487546 ↗, book III (Louisiana), page 461 ↗:

     "You are one night owl, Monsieur Reetchie," he said. / "And you seem to prefer the small hours for your visits, Monsieur de St. Gré," I could not refrain from replying.

3. (musical instrument) A musical instrument which imitates an owl's hoot#Noun|hoot, consisting of a receptacle partly fill#Verb|filled with water#Noun|water and a mouthpiece that is blow#Verb|blown into.

• French: couche-tard, noctambule, oiseau de nuit
• German: Nachteule, Nachtschwärmer, Nachtmensch
• Italian: nottambulo, nottolone
• Portuguese: coruja, noctâmbulo, noctívago
• Russian: полуно́чник
• Spanish: ave nocturna, noctámbulo, noctívago, trasnochador