The Collaborative International Dictionary of English v.0.48:

Admission \Ad*mis"sion\, n. [L. admissio: cf. F. admission. See
   Admit.]
   1. The act or practice of admitting.
      [1913 Webster]

   2. Power or permission to enter; admittance; entrance;
      access; power to approach.
      [1913 Webster]

            What numbers groan for sad admission there! --Young.
      [1913 Webster]

   3. The granting of an argument or position not fully proved;
      the act of acknowledging something ?serted;
      acknowledgment; concession.
      [1913 Webster]

            The too easy admission of doctrines.  --Macaulay.
      [1913 Webster]

   4. (Law) Acquiescence or concurrence in a statement made by
      another, and distinguishable from a confession in that an
      admission presupposes prior inquiry by another, but a
      confession may be made without such inquiry.
      [1913 Webster]

   5. A fact, point, or statement admitted; as, admission made
      out of court are received in evidence.
      [1913 Webster]

   6. (Eng. Eccl. Law) Declaration of the bishop that he
      approves of the presentee as a fit person to serve the
      cure of the church to which he is presented. --Shipley.
      [1913 Webster]

   Syn: Admittance; concession; acknowledgment; concurrence;
        allowance. See Admittance.
        [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

175 Moby Thesaurus words for "admission":
   Americanization, OK, acceptance, access, acculturation,
   acknowledging, acknowledgment, acquisition, adit, admissibility,
   admission fee, admittance, admitting, adoption, affidavit,
   affiliation, affirmation, allegation, allowance, allowing,
   anchorage, appointment, appreciation, assertion, asseveration,
   assimilation, assumption, attest, attestation, averment,
   avouchment, avowal, baptism, brokerage, carfare, cellarage, charge,
   charges, charter, citizenship by naturalization,
   citizenship papers, completeness, comprehension, comprehensiveness,
   comprisal, compurgation, conceding, concession, confession,
   consent, cover charge, coverage, culture shock, declaration,
   demand, deposition, derivation, disclosure, dispensation,
   divulgement, divulgence, dockage, dues, eligibility, embodiment,
   embracement, encompassment, enlistment, enrollment, entrance,
   entrance fee, entree, entry, envisagement, exaction, exactment,
   exhaustiveness, fare, fee, getting, hire, immission, import,
   importation, importing, inauguration, inclusion, inclusiveness,
   income, incoming, incorporation, induction, infiltration, ingoing,
   ingress, ingression, initiation, input, insertion, insinuation,
   installation, instatement, institution, instrument in proof,
   intake, interpenetration, introduction, introgression,
   intromission, intrusion, investiture, leakage, leave,
   legal evidence, liberty, license, license fee, membership,
   nationalization, naturalization, naturalized citizenship, okay,
   openness, ordination, owning, owning up, papers, participation,
   patent, penetration, percolation, permission, permission to enter,
   pilotage, portage, profession, receipt, receival, receiving,
   reception, recognition, release, revelation, rite of confession,
   salvage, scot, scot and lot, seepage, shot, shrift,
   special permission, statement, storage, sworn evidence,
   sworn statement, sworn testimony, taking, tariff, testimonial,
   testimonium, testimony, ticket, ticket of admission, tolerance,
   toleration, toll, towage, unbosoming, vouchsafement, waiver, way,
   wharfage, whole, witness, word