Yes it is. Merriam-Websters. Springfield Mass. Just drove through there this weekend on the way home from VT.<quoted text>
Websters - of which I have a hard copy right here - is not on line for free....
I used to correspond with the physical sciences editor there back in my technical editing days. Back in the 80s.(I even have a word published and a letter to back up that story!)
Not every word is free online. When you go too deep into stuff (unabridged only type stuff) they ask for $$ But 95% of the words I look up are there.
(And other Websters is a lesser Websters.)