Yes, EXPEDITION is a Scrabble word!

Letter values in Scrabble US: E 1, X 8, P 3, E 1, D 2, I 1, T 1, I 1, O 1, N 1.

Is it a valid word?

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

a military campaign designed to achieve a specific objective in a foreign country
an organized group of people undertaking a journey for a particular purpose
a journey organized for a particular purpose
a journey taken for pleasure
the property of being prompt and efficient

Also: military expedition, hostile expedition, pleasure trip.