IPA: /ˈblɒtʃɪli/
KK: /ˈblɑːtʃɪli/
In a way that shows irregular patches or spots, often of different colors or shades.
The paint was applied blotchily, leaving uneven patches on the wall.
Blotchily is formed from "blotch" (from Middle English "blotche", meaning a spot or stain) and "-ily" (a suffix meaning in a manner). The word describes something that is done in a manner that leaves spots or stains.
Think of a 'blotch' as a spot or stain, and remember that 'blotchily' means doing something in a way that leaves spots.