This "what the" is a fairly small photo, which makes it difficult to make out some of the details, and honestly, I think we all ought to be thankful for that fact.
I'm marking this as "swimwear", though to tell the truth, I'm not 100% sure it's meant to be swum in. (Wear this in public-- in the bright light of day-- poolside or at the beach? Seriously?)
But what else could it be?
Something for the bedroom, perhaps. . . though I pity the poor man who's expected to keep a straight face when his lady saunters in wearing a daffodil bikini. ("Let's just switch the lights off first, shall we, Sweetums?")