Need some help with GRE vocab

So I’ve been following the one month plan for a few days now, and came across the homework that says to find 5 GRE level synonyms for some given words.
And in order to do that, the methodology I follow is:

  1. Google " definition"
  2. Take a look at the list of the synonyms
  3. Search if they’re present in Greg’s 960 word list

But the problem I face is there aren’t enough direct GRE-level synonyms of that word. And if I start searching the synonyms of the synonyms, I worry that will actually differ a bit from the original word.
For example, in searching synonyms for “cursory”, i was able to find “perfunctory”, “desultory”, “superficial” and “haphazard”.
I needed one more and so I tried looking for synonyms of these words, but that ends up with words that seem different than “cursory”.

So just wanted to ask if anyone has a better way of going about this? Would appreciate it