also: がへい
noun
something useless; pie in the sky
Literally 'picture of rice cakes,' used metaphorically for something that looks good but has no practical value or cannot be realized. Often appears in the set phrase 画餅に帰す (to come to nothing).
See also: 画餅に帰す (がべいにきす)
その計画は結局画餅に終わった。
That plan ended up being just a pie in the sky.
彼の夢は画餅に過ぎなかった。
His dream was nothing more than a castle in the air.
A more common, colloquial expression with the same literal meaning and metaphorical use. 画餅 is a Sino-Japanese equivalent, more formal and literary.
From Chinese 畫餅 (huàbǐng), literally 'drawn rice cake,' a metaphor for something that cannot satisfy real needs. The Japanese reading がべい is the go-on reading of the characters.