The Collaborative International Dictionary of English v.0.48:

Atelier \A`te*lier"\n. [F.]
   A workshop; a studio.
   [1913 Webster]

WordNet (r) 3.0 (2006):

atelier
    n 1: a studio especially for an artist or designer [syn:
         artist's workroom, atelier]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "atelier":
   agency, barbershop, beauty parlor, beauty shop, bench,
   butcher shop, company, concern, corporation, desk, establishment,
   facility, firm, gallery, house, installation, institution, library,
   loft, office, organization, parlor, sail loft, shop, stacks,
   studio, study, sweatshop, work site, work space, workbench,
   workhouse, working space, workplace, workroom, workshop,
   worktable