"Jeans pocket" refers to the small fabric pouch that is typically sewn into a pair of jeans to hold small items such as coins, keys, or a phone. Full definition
If you're in the habit of dropping your phone in your front jeans pocket, or your inside jacket pocket, you'll immediately notice the difference. (slashgear.com)
Yes, the sizes of jeans pockets will vary, and other questions arise such as the availability of pockets. (librarycity.org)
I either carried the device in hand or placed it in my back jeans pocket while cruising the mall for hours. (gigaom.com)