I don't think of planets in terms of things. Even when I slide into it after almost 50 years of knowing better, I try to catch myself and drag myself out of it. Pluto is surely the one planet easiest to avoid doing that with, because, while referring to something quite real, does not pertain to anything day-to-day.
It is easier to describe Plutonian events because the are staggering, displacing, against the odds, etc. This doesn't exactly translate into behavior when we find Pluto prominent in the birth chart, though.
If I were to reduce it to a single word today (on a different day I might pick a different word) it would be unconditional. Pluto is that which is unbeholden to conditions.
Psychologically, Pluto refers to authenticity needs - the desire to be authentically oneself, unhampered by others. It isolates and distinguishes; dislikes labels, categorization, and arbitrary expectations; is eccentric, extreme, separating, disruptive, and antisocial, marking the exception singled out from the statistical, social, and cultural norm.
So, if we were to give it a noun to be, it would be the uncompromisable existential seed-essence of a being.