A fantastic, impracticable plan or desire
From this point a large area of open water was seen which was believed to be an "open Polar Sea," a chimera which played an important and delusive role in subsequent explorations.
Vanquishing world child hunger and starvation might only be a chimera.
Although she is quite ambitious about world peace, it's likely a chimera of an ideal.
The economic system that he so highly values is a chimera.
The chimera is a mysterious mythical creature, only a fable.