mirage

Concise Oxford English Dictionary © 2008 Oxford University Press:
mirage /ˈmɪrɑːʒ, mɪˈrɑːʒ/

▶noun

• 1 an optical illusion caused by atmospheric conditions, especially the appearance of a sheet of water in a desert or on a hot road caused by the refraction of light from the sky by heated air.

• 2 an unrealistic hope or wish that cannot be achieved.

– origin C19: from Fr., from se mirer ‘be reflected’, from L. mirare ‘look at’.