What is an Introspective Word™?

_{This is in the spirit of the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles.}

If a word conforms to a special rule, I call it an Introspective Word™.

Use the following examples below to find the rule.

And, if you want to analyze, here is a CSV version:

Introspective Words™,Not Introspective Words™
BRIEF,LONG
CLEAR,FUZZY
COMMON,RARE
COMPLETE,INCOMPLETE
ELOQUENT,MOVING
ENGLISH,FRENCH
ESOTERIC,SECRET
ISOGRAM,PANGRAM
MEANINGFUL,RANDOM
NOUN,VERB
SIMPLE,COMPLEX
UNAMBIVALENT,CONFUSED
UNHYPHENATED,HYPHENATED
WEE,LARGE