NOUN (2)

1. any very successful means of achieving a result;

2. a magical command; used by Ali Baba;

The Collaborative International Dictionary of English v.0.48:

Sesame \Ses"a*me\, n. [L. sesamum, sesama, Gr. ????, ???: cf. F.
   s['e]same.] (Bot.)
   Either of two annual herbaceous plants of the genus Sesamum
   (Sesamum Indicum, and Sesamum orientale), from the seeds
   of which an oil is expressed; also, the small obovate,
   flattish seeds of these plants, sometimes used as food. See
   Benne.
   [1913 Webster]

   Open Sesame, the magical command which opened the door of
      the robber's den in the Arabian Nights' tale of "The Forty
      Thieves;" hence, a magical password.

   Sesame grass. (Bot.) Same as Gama grass.
      [1913 Webster]

WordNet (r) 3.0 (2006):

open sesame
    n 1: any very successful means of achieving a result
    2: a magical command; used by Ali Baba

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "open sesame":
   Rasputin, Svengali, VIP, abracadabra, access, bad influence,
   big wheel, bottle opener, can opener, church key, clavis,
   conjuration, corkscrew, countersign, court, eminence grise,
   five-percenter, friend at court, good influence, gray eminence,
   heavyweight, hidden hand, hocus-pocus, incantation, influence,
   influence peddler, influencer, ingroup, key, kingmaker, latchkey,
   latchstring, lobby, lobbyist, lords of creation, magic formula,
   magic words, man of influence, manipulator, master key,
   mumbo jumbo, opener, passkey, password, powers that be,
   pressure group, secret grip, shibboleth, sinister influence,
   skeleton key, special interests, special-interest group, tessera,
   the Establishment, ticket, tin opener, token,
   very important person, watchword, wheeler-dealer, wire-puller