The Collaborative International Dictionary of English v.0.48:

Well-known \Well"-known`\, a.
   Fully known; generally known or acknowledged.
   [1913 Webster]

         A church well known with a well-known rite. --M.
                                                  Arnold.
   [1913 Webster]

WordNet (r) 3.0 (2006):

well-known
    adj 1: widely or fully known; "a well-known politician"; "well-
           known facts"; "a politician who is well known"; "these
           facts are well known"
    2: frequently experienced; known closely or intimately; "a long-
       familiar face"; "a well-known voice reached her ears" [syn:
       long-familiar, well-known(a)]

Moby Thesaurus II by Grady Ward, 1.0:

69 Moby Thesaurus words for "well-known":
   acclaimed, back-number, banal, bewhiskered, bromidic, celebrated,
   common, commonly known, commonplace, conspicuous, corny, current,
   cut-and-dried, distinguished, fabled, fade, famed, familiar,
   famous, far-famed, far-heard, fusty, hackney, hackneyed, honored,
   household, important, leading, legendary, marked, moth-eaten,
   much acclaimed, musty, mythical, notable, noted, notorious,
   of mark, of note, old hat, outstanding, platitudinous, popular,
   prominent, proverbial, public, renowned, set, square, stale,
   stereotyped, stock, talked-about, talked-of, threadbare, timeworn,
   trite, truistic, universally admitted, universally recognized,
   unoriginal, warmed-over, well-kenned, well-recognized,
   well-understood, well-worn, widely known, worn, worn thin