IPA: /ˈtʃɪəfʊlə/
KK: /ˈtʃɪrflər/
More happy and positive than usual; showing a greater level of joy or optimism.
She felt cheerfuller after receiving the good news about her job.
Comparative: cheerfuller
Superlative: cheerfullest
Cheerfuller → It is formed from "cheer" (from Old French *chiere*, meaning face or countenance, which evolved to mean mood or spirit) and "-ful" (meaning full of) and "-er" (a suffix used to form comparative adjectives). The word "cheerfuller" means more full of cheer or happiness than something else.
Think of someone who is 'full of cheer' and then imagine comparing them to someone else — that's why 'cheerfuller' means more cheerful.
No commonly confused words.