In the United States, any work published before 1923 is in the public domain (= not under copyright). For more information, see the detailed chart on the duration of copyrights in the U.S. at...
If something is abridged it means that it has been made shorter/simpler - parts have been left out. Therefore an unabridged dictionary would be a complete dictionary of a language.
It is the same thingNoah Webster was an American lexicographer who published the first American dictionaryCharles and George Merriam began revising and publishing Webster's work in 1840. they later...
"Webster's" is applied to dictionaries of American English, based on the one first published in the US by Noah Webster in 1806, as "A Compendious Dictionary of the English Language".