Having posted on euphemisms, the obvious next post is purple prose.
One person's purple prose is another person's lush description. For me, if it "throbs", it's purple. Doesn't matter if the thing pulsating is genitalia, machinery or alien lifeforms, throbs is a warning sign of authorial enthusiasm. [When hearts throb, they're cliched.]
That's the thing with purple prose, I think it sneaks in to what the author considers a vital scene. Whether this is because the author knows the scene is important, but has run out of steam and compensates by over-writing, or because the author is just so damn enthusiastic that their keyboard runs away with them, I don't know. When a whole book is purple prose, well, unless you like that sort of thing, the best action is to walk away quietly. You don't want that purple exploding and flinging magenta and violet gunk everywhere.
Of course, editors are meant to safeguard readers from purple prose.
As a writer, first you have to catch your editor, and purple prose is a major handicap. Editors are wary creatures. Purple prose is like hunting them with bells on all your toes and fingers. You give the wary editor way too much warning, and they run.
So, how do you identify purple prose when you've written it and it glows with perfection (in your eyes)?
If I knew the answer to that question, I wouldn't write the damn stuff. My opinion, for what it's worth, is that purple prose shows up as redundancy. If it's open to parody, you're stepping on throbbing ground. If it's so bright you have to wear sunglasses, you might want to tone it down--use the filter of "keep it real".
Writing poetry and submitting it for open critique is a useful method of identifying and stripping purple prose.