'under the jacket' is correct and usable in written English.
You can use it to describe something or someone that is hidden beneath a jacket. For example, "I felt something lumpy under the jacket, so I removed it to discover a wallet."
"I knew something under the jacket was alive," he said.
In the drawer was a pajama jacket, and under the jacket was the album.
The average fire-induced electrical failure temperature under the jacket of the CCV cable was approximately 400 °C.
Feathers rose high in the hair; they were worn like a tutu under the jacket of a pinstriped pantsuit.
He wore a dark cap, a black leather jacket, blue jeans and a purple hooded sweatshirt under the jacket.
If a title is eligible for examination in either digital or print format, buttons will be present under the jacket image on the book's page as illustrated below.
Sometimes he forgot about the dress, showing only tights under the jackets, which is the significant look for many young women.
I can't see him but I can see lots of stern-faced men in black with their fingers to their ear and mysterious bulges under the jackets.
But strong winds blew ash from the fireworks on to the guests, driving the many women in low-cut dresses to shelter under the jackets of obliging males.No sooner was the party over than it seemed that the industry itself might have to run for cover, as the price bubble that had seen bulk-shipping rates more than double since September 2003 suddenly lost air.
When Kate Moss wears simple ballet pumps on the school run – styled with perfect jeans, an under-the-radar but fabulously tailored jacket, and yesterday's blowdry by a world-class hairdresser on some fabulous shoot – she looks amazing.
In Riverside Park he played ball until dusk, carefully laying the jacket under a tree.
