IPA: //ˈfruːt.fʊl.ər//
KK: /ˈfruːtˌfʊlər/
More productive or yielding better results than something else.
The new methods proved to be fruitfuller than the old ones in increasing crop yields.
Comparative: fruitfuller
Superlative: fruitfullest
Fruitfuller → It is formed from "fruit" (from Old French *fruit*, meaning produce or yield) and "-ful" (meaning full of) combined with the comparative suffix "-er" (indicating more). The word "fruitfuller" means more full of fruit or yielding more produce than something else.
Think of 'fruit' as something that yields produce, and '-ful' means full of, while '-er' indicates more. So, 'fruitfuller' means yielding more fruit.
No commonly confused words.