Yes, AMBROSIA is a Scrabble word!

Letter values in Scrabble US: A 1, M 3, B 3, R 1, O 1, S 1, I 1, A 1.

Is it a valid word?

AMBROSIA is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a mixture of nectar and pollen prepared by worker bees and fed to larvae
any of numerous chiefly North American weedy plants constituting the genus Ambrosia that produce highly allergenic pollen responsible for much hay fever and asthma
fruit dessert made of oranges and bananas with shredded coconut
(classical mythology) the food and drink of the gods; mortals who ate it became immortal