chimera
[noun]
Synonyms: pipe dream, bubble, dream, fantasy (or phantasy), illusion, pipe, rainbow

[TahlilGaran] English Synonym Dictionary ▲

chi‧me‧ra , chimaera /kaɪˈmɪərə, kə- $ -ˈmɪrə/ noun [countable]
[Date: 1300-1400; Language: Latin; Origin: chimaera, from Greek chimaira 'female goat, chimera']

1. formal something, especially an idea or hope, that is not really possible and can never exist:
trying to present that chimera, ‘a balanced view’

2. an imaginary creature that breathes fire and has a lion’s head, a goat’s body, and a snake’s tail

3. technical a living thing that contains cells from another living thing

[TahlilGaran] Dictionary of Contemporary English ▲