The Collaborative International Dictionary of English v.0.48:

Time-honored \Time"-hon`ored\ (t[imac]m"[o^]n`[~e]rd), a.
   Honored for a long time; venerable, and worthy of honor, by
   reason of antiquity, or long continuance.
   [1913 Webster]

WordNet (r) 3.0 (2006):

time-honored
    adj 1: acceptable for a long time; "time-honored customs" [syn:
           time-honored, time-honoured]
    2: honored because of age or long usage; "time-honored
       institutions" [syn: time-honored, time-honoured]

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "time-honored":
   accepted, acknowledged, admitted, age-old, august, awe-inspiring,
   awesome, awful, conformable, consuetudinary, conventional, current,
   customary, dreadful, established, estimable, everyday, familiar,
   fixed, folk, generally accepted, habitual, hallowed, handed down,
   heroic, hoary, honorable, honored, immemorial, inveterate,
   legendary, long-established, long-standing, mythological, normal,
   obtaining, of long standing, of the folk, oral, ordinary, popular,
   prescribed, prescriptive, prevalent, received, recognized, regular,
   regulation, respected, revered, reverend, rooted, set, standard,
   stock, traditional, tried and true, true-blue, understood,
   unwritten, usual, venerable, venerated, widespread, wonted,
   worshipful