The Collaborative International Dictionary of English v.0.48:

Rach \Rach\, Rache \Rache\ (r[a^]ch), n. [AS. r[ae]cc; akin to
   Icel. rakki.] (Zool.)
   A dog that pursued his prey by scent, as distinguished from
   the greyhound. [Obs.]
   [1913 Webster]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

RACH
       Random Access CHannel (GSM, CCCH, mobile-systems)