from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A trial exercise; a rehearsal.
- n. A test exercise in combat skills without the use of live ammunition.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A practice; a rehearsal.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a practice session in preparation for a public performance (as of a play or speech or concert)
dry (in the slang sense of "impotent" or "harmless") + run. First attested in print in 1941, but apparently much older in spoken English. (Wiktionary)