Yes, HOTDOG is a Scrabble word!

Letter values in Scrabble US: H 4, O 1, T 1, D 2, O 1, G 2.

Is it a valid word?

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

someone who performs dangerous stunts to attract attention to himself
a frankfurter served hot on a bun
a smooth-textured sausage of minced beef or pork usually smoked; often served on a bread roll

Also: hot dog, red hot.