The Collaborative International Dictionary of English v.0.48:

Arsenal \Ar"se*nal\ ([aum]r"s[-e]*nal), n. [Sp. & F. arsenal
   arsenal, dockyard, or It. arzanale, arsenale (cf. It. &
   darsena dock); all fr. Ar. d[=a]r[,c]in[=a]'a house of
   industry or fabrication; d[=a]r house + [,c]in[=a]'a art,
   industry.]
   A public establishment for the storage, or for the
   manufacture and storage, of arms and all military equipments,
   whether for land or naval service.
   [1913 Webster]

WordNet (r) 3.0 (2006):

arsenal
    n 1: all the weapons and equipment that a country has [syn:
         arsenal, armory, armoury]
    2: a military structure where arms and ammunition and other
       military equipment are stored and training is given in the
       use of arms [syn: arsenal, armory, armoury]
    3: a place where arms are manufactured [syn: armory,
       armoury, arsenal]

Moby Thesaurus II by Grady Ward, 1.0:

109 Moby Thesaurus words for "arsenal":
   ammo dump, archives, armory, artillery park, assembly line,
   assembly plant, atomic arsenal, atomic energy plant, attic, bank,
   basement, bay, bin, bindery, boatyard, boilery, bonded warehouse,
   bookbindery, bookcase, box, brewery, brickyard, bunker, buttery,
   cannery, cargo dock, cellar, chest, closet, conservatory, crate,
   creamery, crib, cupboard, dairy, defense plant, depository, depot,
   distillery, dock, dockyard, drawer, dump, exchequer, factory,
   factory belt, factory district, feeder plant, flour mill,
   glory hole, godown, gun park, hold, hutch, industrial park,
   industrial zone, library, locker, lumber room, lumberyard, magasin,
   magazine, main plant, manufactory, manufacturing plant,
   manufacturing quarter, mill, mint, munitions plant, oil refinery,
   packing house, park, plant, pottery, power plant, production line,
   push-button plant, rack, refinery, repertory, repository,
   reservoir, rick, sawmill, shelf, shipyard, stack, stack room,
   stock room, storage, store, storehouse, storeroom,
   subassembly plant, sugar refinery, supply base, supply depot, tank,
   tannery, treasure house, treasure room, treasury, vat, vault,
   warehouse, wine cellar, winery, yard, yards