This Google search reveals a collection of links (from searching using the Readers Digest “It pays to increase your Word Power” search-string) this kind of information, was available and very popular years ago when the internet did not exist and the Readers Digest magazine had a list of less well known words each month.
You will need to click the top link twice, as it seems the information has moved. The Quizlet set of words is also really useful and on the extra links at the end of the page, there is a link through to a downloadable file.
For meanings in sentences of words you are not familiar with, try substituting (replacing) the unknown word to see if you can gain an insight to understanding when you dont have access to a dictionary.
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