First recorded in 1905–10; formerly a trademark
A thermos is a portable container that keeps liquids hot or cold for a long time. When you go ice skating, you may want to bring along a thermos of hot chocolate. Officially, the word Thermos is spelled with a capital T, since like Band-Aid and Kleenex, it's actually a trademarked brand name. Still, it's common to refer to vacuum flasks (even those not made by the Thermos company) generally as thermoses. The very first thermos was made in 1892, and they were produced commercially starting in 1904. In Greek, the word thermos means "hot."
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
You could drop off breakfast in the form of convenience-store pastries and a thermos of hot coffee to share.
From Salon • Jan. 19, 2026
At regular intervals, he poured himself a cup of steaming hot chai from his thermos.
From Slate • Jan. 3, 2026
The thermos still sells on the Stanley website for $36.
From Seattle Times • Jan. 12, 2024
When I was growing up, the holidays meant no school, which gave me the chance to curl up on the couch in a robe and fuzzy socks while drinking hot chocolate from a red thermos.
From New York Times • Nov. 15, 2023
By the time I was finished making lunch and got myself dressed, Dad had fixed his thermos of coffee and was ready to go, too.
From "Red Kayak" by Priscilla Cummings
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
