The Collaborative International Dictionary of English v.0.48:

Virtu \Vir*tu"\ (?; 277), n. [It. virt[`u] virtue, excellence,
   from L. virtus. See Virtue.]
   A love of the fine arts; a taste for curiosities. --J.
   Spence.
   [1913 Webster]

   An article of virtu, or a piece of virtu an object of art
      or antiquity; a curiosity, such as those found in museums
      or private collections.
      [1913 Webster]

            I had thoughts, in my chambers to place it in view,
            To be shown to my friends as a piece of virt[`u].
                                                  --Goldsmith.
      [1913 Webster]

WordNet (r) 3.0 (2006):

virtu
    n 1: love of or taste for fine objects of art [syn: virtu,
         vertu, connoisseurship]
    2: artistic quality [syn: virtu, vertu]
    3: objet d'art collectively (especially fine antiques)

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "virtu":
   aesthetics, art, art object, artistic skill, artistic taste,
   artistry, arty-craftiness, brainchild, bric-a-brac, classic,
   composition, connoisseurship, creation, design, dilettantism,
   epicureanism, epicurism, expertise, expertism, flair, friandise,
   gastronomy, grotesque, kitsch, master, masterpiece, masterwork,
   mobile, museum piece, nude, old master, pasticcio, pastiche, piece,
   piece of virtu, stabile, statue, still life, study, talent,
   virtuosity, work, work of art