"Deep indentation" refers to a noticeable and significant dent or hollow that is formed on the surface of an object, usually due to pressure or force being applied. Full definition
Online it's seldom chatted about and the biggest complaint I've read is the leaving deep indentations in the skin. (simplymombailey.com)
Deep indentations in the doors and roof reflect the Corvette's influence. (automobilemag.com)
The hard, yellow green underside of its thorax ismarked with deep indentations that resemble smiley faces doubled anddistorted in mirrors. (discovermagazine.com)