Yes, HOROSCOPE is a Scrabble word!

Letter values in Scrabble US: H 4, O 1, R 1, O 1, S 1, C 3, O 1, P 3, E 1.

Is it a valid word?

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

a prediction of someone's future based on the relative positions of the planets
a diagram of the positions of the planets and signs of the zodiac at a particular time and place