1. Suru verb, Adverb (fukushi)

   to be disappointed; to be dejected; to be downhearted; to be discouraged; to be disheartened; to lose heart; to feel let down

   Onomatopoeic or mimetic word

   その知らせにはがっかりだ。

2. to feel exhausted; to feel drained

   Onomatopoeic or mimetic word

Also written ガッカリgakkari