Yes, JACTITATION is a Scrabble word!

Letter values in Scrabble US: J 8, A 1, C 3, T 1, I 1, T 1, A 1, T 1, I 1, O 1, N 1.

Is it a valid word?

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

speaking of yourself in superlatives
(law) a false boast that can harm others; especially a false claim to be married to someone (formerly actionable at law)
(pathology) extremely restless tossing and twitching usually by a person with a severe illness

Also: self-praise.