A department store fitting room. The clerk steps back, tilts her head, and delivers the highest compliment in her vocabulary: "わあ、スマートですね!"
You check your face in the mirror. You have said nothing clever. You have not, in fact, spoken at all — you have just tried on a blazer.
She is not talking about your mind. She is talking about the line of your shoulders in that jacket, and specifically how not-wide you currently look.
In everyday use スマート means slim, trim, sleek — a slender build, a jacket that skims rather than bulges, a haircut that reads tidy rather than intelligent. スマートな体型 is a slim figure. もっとスマートに見せたい is "I want to look slimmer", said in fitting rooms and diet-app onboarding screens across the country. None of it has anything to do with your test scores.
This is not Japan mishearing English so much as Japan keeping an older English meaning that English itself has mostly let go of. Long before "smart" settled on "clever", it meant sharp, trim, neatly turned-out — a smart uniform, a smart little cottage, a person smartly dressed. Japan imported the word during the Meiji era through exactly that register: fashion writing, tailoring, department-store advertising describing a stylishly slender silhouette. The clothes carried the word in, and the word quietly narrowed to describe the body inside the clothes.
You can still see the older sense surviving untouched in one specific corner: スマートカジュアル, the dress-code term for the tier between full formality and jeans-and-a-t-shirt, used for weddings, nice restaurants and hotel dining rooms. That phrase means almost exactly what "smart casual" means on a British invitation — neat, polished, put-together. Japan didn't get that one wrong at all. It's the same word doing the same job it always did, just standing next to a version of itself that has drifted a long way down the street.
Meanwhile the "clever" sense of smart never actually left Japanese — it just moved into a single compound and stayed there. スマートフォン means smartphone precisely because it's an intelligent, multi-function phone, not a slender one, and every Japanese speaker switches between the two meanings without noticing there even are two. Ask someone what スマート means and they'll say slim. Ask what makes a phone スマート and they'll say it's clever. Nobody in the room considers this a contradiction, because nobody in the room has ever had to hold both senses in the air at the same time before answering.
English simplified. "Smart" used to mean sharp, neat, trim, and then somewhere in the last century the culture let that reading fade and let "clever" take over the whole word almost by itself. Japan never got that memo, because it imported "smart" a hundred-plus years ago and then filed the two senses into separate rooms — one for bodies and tailoring, one for phones — instead of merging them the way English did. The result is a language technically carrying more of the original word than the country that invented it, split cleanly enough that the split itself is invisible from the inside.