The phrase "deep creases" means very noticeable or significant lines or folds in something, like wrinkles on someone's face or folds in a piece of fabric. Full definition
You see that ridiculously deep crease in between his eyes? (sbnation.com)
They are joined to the housings of the circular fog lamps by deep creases that echo the hexagonal blacked - out grille that is both larger and more sinister - looking than the non-turbo Veloster's. (cnet.com)
For 2019, the X4 gets some subtle styling tweaks, including a new front fascia, deeper creases along its flanks, and new taillights. (digitaltrends.com)