You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.
Start your free trial today and get unlimited access to America's largest dictionary, with:
“Arseno-.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/arseno-. Accessed 4 Feb. 2023.
Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!
See Definitions and Examples »
Get Word of the Day daily email!
The Great British Vocabulary Quiz
Test your knowledge - and maybe learn something along the way.
Can you make 12 words with 7 letters?
A lexicographer's best friend
More words, more beautiful, more useless
Spelling isn't all black and white.
Look up any year to find out
One goose, two geese. One moose, two... moose. Wh...
It is in fact a real word (but that doesn't mean ...
Both words imply motion, but the difference may b...
The fascinating story behind many people's favori...
Can you name these antiquated items?
Take the quiz
"Leggings" or "mom jeans"? "Chillax" or "dumpster...
Test your knowledge - and maybe learn something a...
Can you outdo past winners of the National Spelli...