The Smarandache's Synonymity Test:
similar to, and an extension of, the antonym test in psychology,
is a verbal test where the subject must supply as many as possible synonyms
of a given word (W), in a given language (L), within a as short as possible period
of time (t).
How to measure it?
The spectrum of supplied word synonyms (s) provided by the subject, with respect
to the total number of that word synonyms (S) existing in that given language,
within the measured period of time (t),
shows the subject's level of linguistic synonym proficiency:   s/S/t = s/(S·t).

George Hammond mentioned that "this test is more related to Intelligence than to
Personality" and "besides having a high loading on IQ (or psychometric-g) it might
also have a number of specific factors, such as Reading Level, in a factor analysis
procedure".  "(...) if you gave such a test to a group of subjects, and also included
tests for Intelligence, Personality, Reading Ability, etc. and then factored the
resulting correlation matrix, I think you would find the highest loading on Reading
Level, then IQ, then Personality".