Cronut is one of the rare food words with a birth certificate: a named inventor, a dated launch and a global craze that followed. It is also a trademark, which explains the strange wording you see on menus.
A croissant that thinks it is a doughnut
A cronut is a ring-shaped pastry made from laminated croissant dough, fried like a doughnut and usually filled and glazed.

Merriam-Webster defines it exactly as a fried pastry made from croissant dough. The layers are the giveaway: cut one open and it flakes like a croissant while eating like a doughnut, typically with flavoured cream inside and a sugared or glazed finish.
A dated word with a documented birth
The word was coined in 2013 when pastry chef Dominique Ansel created the pastry in New York, and the craze spread worldwide that year.
Wikipedia documents the May 2013 launch at the Dominique Ansel Bakery in SoHo, and National Geographic covered the queues and copycats as the craze went global. Unlike old food words, this one has a named inventor and date, which makes it a satisfying piece of menu vocabulary.
Why menus say cronut-style
Cronut is a trademark, which is why many menus use wording like cronut-style or croissant doughnut for their own versions.
Dictionary listing and trademark protection coexist without conflict: the word is in the dictionary, and the pastry name is registered to its creator. That is why a cafe selling its own version writes something adjacent rather than the bare word, and why capitalisation survives in careful writing.
FAQ
Is cronut a real dictionary word?
Yes, it appears in major dictionaries, though the pastry name remains a registered trademark.
What does it taste like?
Flaky and buttery like a croissant with the fried richness of a doughnut, plus cream filling in the original style.
How should I write it on my cafe menu?
Use the trademark word only for the licensed product; otherwise describe it as a croissant doughnut.