IPA: /ˈɡrɪmiər/
KK: /ˈɡrɪmɪər/
More dirty or covered with grime than something else.
The old building looked grimier than the new one next to it.
Grimier → It is formed from "grim" (from Old English *grim*, meaning fierce or cruel) and "-ier" (a comparative suffix indicating more). The word "grimier" means more grim or more fierce in nature.
Think of something that is 'more fierce' or 'more cruel' — 'grim' describes a harsh quality, and '-ier' shows that it is to a greater degree.