IPA: /ˈmɔɪstər/
KK: /ˈmɔɪstər/
Having more moisture; slightly wet or damp.
The cake turned out moister than I expected, making it very delicious.
Comparative: moister
Superlative: moistest
Moister is formed from "moist" (from Old French *moiste*, meaning slightly wet or damp) and the suffix "-er" (meaning more). The word "moister" means more damp or wet than something else.
Think of something that is 'more damp' — 'moist' means slightly wet, and '-er' indicates a comparison.