Yes, MONOCRACY is a Scrabble word!

Letter values in Scrabble US: M 3, O 1, N 1, O 1, C 3, R 1, A 1, C 3, Y 4.

Is it a valid word?

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

a form of government in which the ruler is an absolute dictator (not restricted by a constitution or laws or opposition etc.)

Also: authoritarianism, one-man rule.

Not playable in Scrabble US: STALINISM.