The Collaborative International Dictionary of English v.0.48:

Assignment \As*sign"ment\, n. [LL. assignamentum: cf. OF.
   assenement.]
   1. An allotting or an appointment to a particular person or
      use; or for a particular time, as of a cause or causes in
      court.
      [1913 Webster]

   2. (Law)
      (a) A transfer of title or interest by writing, as of
          lease, bond, note, or bill of exchange; a transfer of
          the whole of some particular estate or interest in
          lands.
      (b) The writing by which an interest is transferred.
      (c) The transfer of the property of a bankrupt to certain
          persons called assignees, in whom it is vested for the
          benefit of creditors.
          [1913 Webster]

   Assignment of dower, the setting out by metes and bounds of
      the widow's thirds or portion in the deceased husband's
      estate, and allotting it to her.
      [1913 Webster]

   Note: Assignment is also used in law as convertible with
         specification; assignment of error in proceedings for
         review being specification of error; and assignment of
         perjury or fraud in indictment being specifications of
         perjury or fraud.
         [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

212 Moby Thesaurus words for "assignment":
   abalienation, accession, accounting for, agency, agentship,
   alienation, allocation, allotment, amortization, amortizement,
   anointing, anointment, answerability, application, appointment,
   apportionment, appropriation, arrogation, ascription, assignation,
   assumption, attachment, attribution, authority, authorization,
   bargain and sale, barter, bequeathal, blame, brevet, busywork,
   care, cession, chalk talk, chare, charge, chore, collocation,
   commendation, commission, commissioning, commitment, conferment,
   conferral, connection with, consecration, consignation,
   consignment, conveyance, conveyancing, coronation, credit, cure,
   deeding, delegated authority, delegation, deliverance, delivery,
   demise, denomination, deployment, deposit, deposition, deputation,
   derivation from, designation, determination, devoir, devolution,
   devolvement, discourse, disposal, disposition, disquisition,
   distribution, duty, earmarking, election, embassy, emplacement,
   empowerment, enfeoffment, entrusting, entrustment, errand,
   etiology, exchange, executorship, exequatur, exercise, exposition,
   factorship, fish to fry, fixing, full power, giving, giving out,
   harangue, homework, homily, honor, imputation, incumbency,
   infeodation, infeudation, instruction, job, job of work,
   jurisdiction, labor, lading, lease and release, lecture,
   lecture-demonstration, legation, legitimate succession, lesson,
   liability, license, lieutenancy, loading, localization, locating,
   location, make-work, mandate, matters in hand, mission, moral,
   moral lesson, morality, moralization, naming, nomination,
   object lesson, obligation, odd job, office, ordainment, ordination,
   packing, palaetiology, piece of work, pinning down, pinpointing,
   placement, placing, plenipotentiary power, position, positioning,
   post, posting, power of attorney, power to act, preachment,
   precision, procuration, project, proxy, purview, putting, recital,
   recitation, reference to, regency, regentship, relegation,
   remanding, reposition, responsibility, saddling, sale, seizure,
   selection, sermon, service, set task, setting aside, settlement,
   settling, signification, situation, skull session, specification,
   spotting, stationing, stint, stipulation, storage, stowage,
   succession, surrender, tabbing, tagging, taking over, talk, task,
   teaching, things to do, trading, transfer, transference,
   transferral, transmission, transmittal, trust, trusteeship,
   usurpation, vesting, vicarious authority, warrant, work