Newsflash: There cannot be varying degrees of uniqueness. Being unique is a binary situation... like pregnancy. You either are or you aren't. A thing either is unique or it isn't. This concept resurfaced today as I was going through my e-mail and encountered this spammy subject header: "The Most Unique Lamps You'll See at M&O 💡" Here we go again...
Now, even the language mavens at the venerable Merriam-Webster Dictionary are bending a bit on "unique"'s definition, slouching into the position (in the third citation) where they consider it synonymous with "unusual." The editors pinpoint a line from a J. D. Salinger story, "For Esmé—with Love and Squalor," to buttress their point: "we were fairly unique, the sixty of us, in that there wasn't one good mixer in the bunch." I like Salinger's writing as much as anyone who read him as a teenager, but I have to draw the line at this fraudulent usage.
This may shock you, but I'm siding with the staunch guardians of English at Rutgers University, who proclaim with daunting authority: "Unique means 'one of a kind.' There are no degrees of uniqueness: something is unique, or it is not. If you want a word that admits degrees, use special or unusual."
Ross Petras and Kathryn Petras, authors of a forthcoming book titled That Doesn't Mean What You Think It Means: The 150 Most Commonly Misused Words and Their Tangled Histories (Ten Speed Press; out September 4), concur. Unfortunately, they are pessimistic about getting people out of the habit of using "unique" incorrectly. A recent Google search conducted by the Petrases yielded 772,000 entries for "'one of the most unique restaurants,' along with hundreds of thousands of other not-so-unique uniques. Maybe we'll start saying 'one-of-a-kind' instead. Then again, there'll probably soon be ads for 'one of the most one-of-a-kind restaurants ever!'"
From now on, when you hear folks say something like, "That shirt is so unique," ask them, "Oh, really? How unique is it?" and then watch them hem and haw. You may lose friends, but you'll win another battle in the language war, and that's what really matters.