IPA: /ˈkrɛstˌfɔːlən/
KK: /ˈkrɛstˌfɔlən/
Feeling sad and disappointed, often because of a failure or setback.
After losing the game, the team looked crestfallen as they left the field.
Crestfallen → It is formed from "crest" (from Old French *creste*, meaning the top or peak of something) and "fallen" (the past participle of "fall", meaning to drop down). The word describes someone who has dropped down from a high point, often in spirit or mood, indicating disappointment or sadness.
Think of someone who has lost their 'crest' or peak of happiness and has 'fallen' into a state of sadness — that's what crestfallen means.
No commonly confused words.