1. 
[syn: capaciousness, roominess, spaciousness, commodiousness]
The Collaborative International Dictionary of English v.0.48:
Spacious \Spa"cious\, a. [L. spatiousus: cf. F. spacieux. See
   Space, n.]
   1. Extending far and wide; vast in extent. "A spacious plain
      outstretched in circuit wide." --Milton.
      [1913 Webster]
   2. Inclosing an extended space; having large or ample room;
      not contracted or narrow; capacious; roomy; as, spacious
      bounds; a spacious church; a spacious hall. --
      Spa"cious*ly, adv. -- Spa"cious*ness, n.
      [1913 Webster]
WordNet (r) 3.0 (2006):
spaciousness
    n 1: spatial largeness and extensiveness (especially inside a
         building); "the capaciousness of Santa's bag astounded the
         child"; "roominess in this size car is always a
         compromise"; "his new office lacked the spaciousness that
         he had become accustomed to" [syn: capaciousness,
         roominess, spaciousness, commodiousness]