If you're interested in American English, then you are probably familiar with Webster's Revised Unabridged Dictionary from 1913. Noah Webster started his American Dictionary a century earlier and I think 1913 is the most recent one that is in the public domain. It has been digitized and you can download it from places like Project Gutenberg and access it online at places like webster's 1913.

You can also get it from Debian via the Collaborative International Dictionary of English (CIDE)

There is a dictd server and dict-gcide contains the GNU version of CIDE.

sudo apt install dictd dict-gcide

I also installed a DICT-formatted version of WordNet and the Jargon file.

sudo apt install dict-wn dict-jargon

Now I have a server for these three dictionaries. Next, I installed a command line client and documentation

sudo apt install dict dict-foldoc

This allows me to look up a word from the command line!

❯ dict popery
2 definitions found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Popery \Pop"er*y\, n.
     The religion of the Roman Catholic Church, comprehending
     doctrines and practices; -- generally used in an opprobrious sense.
     [1913 Webster]

From WordNet (r) 3.0 (2006) [wn]:

      n 1: offensive terms for the practices and rituals of the Roman
           Catholic Church [syn: {popery}, {papism}]

This all started because I am reading the English translation of Independent People and there are lots of words like popery that I don't know.

I also installed a client for Emacs

M-x package-install RET dictionary RET

Now I can look up the word at point in an Emacs buffer with M-x dictionary-search RET. I decided to bind that to a key

(global-set-key (kbd "C-c w") #'dictionary-search)

There is also an Xfce client

screen shot of xfce client