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 has a certain property, I call it a Narcissistic Word™. If it definitively does not have that property, I call it an Echoing Word™.
You can use the examples below to find the property:
$$\begin{array}{|c|c|} \hline \textbf{Narcissistic™}&\textbf{Echoing™}\\ \hline \text{RUDDY}&\text{HEALTHY}\\ \hline \text{CHAOTIC}&\text{DEVILISH}\\ \hline \text{COMPOSED}&\text{DECOMPOSED}\\ \hline \text{COMPOSITE}&\text{VERSATILE}\\ \hline \text{MOSTLY}&\text{SURPASSING}\\ \hline \text{VETERAN}&\text{BANDIT}\\ \hline \text{UPTIGHT}&\text{SHY}\\ \hline \text{NARCISSISTIC}&\text{VAIN}\\ \hline \text{ISOLATED}&\text{RETILEABLE}\\ \hline \text{EXPLAIN}&\text{SCIENTIFIC}\\ \hline \text{REFRESHING}&\text{ROTTEN}\\ \hline \text{DISTASTEFUL}&\text{VENOMOUS}\\ \hline \text{UNCOPYRIGHTABLE}&\text{ANNAGRAMMABLE}\\ \hline \text{VIRIDESCENT}&\text{FANTASTICAL}\\ \hline \end{array} $$
And a CSV version:
RUDDY, HEALTHY
CHAOTIC, DEVILISH
COMPOSED, DECOMPOSED
COMPOSITE, VERSATILE
MOSTLY, SURPASSING
VETERAN, BANDIT
UPTIGHT, SHY
NARCISSISTIC, VAIN
ISOLATED, RETILEABLE
EXPLAIN, SCIENTIFIC
REFRESHING, ROTTEN
DISTASTEFUL, VENOMOUS
UNCOPYRIGHTABLE, ANNAGRAMMABLE
VIRIDESCENT, FANTASTICAL
