(Usenet) Initialism of request for discussion. / Initialism of radio frequency device.

(mineralogy) An altered granite composed of pink orthoclase feldspar, green epidote, and generally colorless quartz.

Someone who splashes. / (dated) A guard to keep off splashes from anything; especially, one of the guards over the wheels of a carriage, locomotive, etc. / (MLE, slang) A knife (for it does wettings).

(biochemistry) A peptide that is derived from part of a larger one