Yes, LIMITER is a Scrabble word!

Letter values in Scrabble US: L 1, I 1, M 3, I 1, T 1, E 1, R 1.

Is it a valid word?

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

(electronics) a nonlinear electronic circuit whose output is limited in amplitude; used to limit the instantaneous amplitude of a waveform (to clip off the peaks of a waveform)