[puro] adj. pure, uncontaminated, untainted; clean, free of dirt; absolute, utter
It is an adjective, "part of speech used to modify a noun". Ergo, it is meaningless without an explicit or implicit noun upon which to act.
A simple test would be, for example, to replace "puro" in a sentence with your chosen definition. For example, let's say we want "puro" to mean "cigar".
I smoked a rockin Nicaraguan cigar today (not bad, but not what you really intended).
Now, let's use one of the words from the definition above.
I smoked a rockin Nicaraguan pure today. Not so good. However, I think that if we made it a real adjective, we get something like this: I smoked a rockin pure Nicaraguan cigar today.
Much better, me thinks.
I tend to slant towards the rules of the Blue Book (
http://www.grammarbook.com/) but can go with the flow for anyone who wants to head in the direction of Strunk and White (original is online here:
http://www.crockford.com/wrrrld/style.html).