The Collaborative International Dictionary of English v.0.48:

check out \check` out"\ v. i.
   1. To vacate a room at a hotel, notel, etc. Converse of
      check in.
      [PJC]

   2. To die. [Colloq.]
      [PJC]

The Collaborative International Dictionary of English v.0.48:

check out \check" out\ v. t.
   1. To inspect or examine. [Colloq.]
      [PJC]

   2. To make a record of having borrowed (something) for
      temporary use; as, to check out a book at the library; to
      check out equipment from a depository.
      [PJC]

   3. To bring (items to be purchased) to a checkout counter
      (as at a supermarket or other retail store) where the
      prices may be totaled and the bill may be paid.
      [PJC]

WordNet (r) 3.0 (2006):

check out
    v 1: examine so as to determine accuracy, quality, or condition;
         "check the brakes"; "Check out the engine" [syn: check,
         check up on, look into, check out, suss out, check
         over, go over, check into]
    2: announce one's departure from a hotel [ant: check in, sign
       in]
    3: be verified or confirmed; pass inspection; "These stories
       don't check!" [syn: check, check out]
    4: trace; "We are running down a few tips" [syn: run down,
       check out]
    5: record, add up, and receive payment for items purchased; "She
       was checking out the apples that the customer had put on the
       conveyer belt"
    6: withdraw money by writing a check [syn: cheque, check
       out]
    7: try to learn someone's opinions and intentions; "I have to
       sound out the new professor" [syn: check out, sound out,
       feel out]

Moby Thesaurus II by Grady Ward, 1.0:

87 Moby Thesaurus words for "check out":
   audit, autopsy, balance, balance the books, buy it, canvass,
   cash in, check, check and doublecheck, check in, check over,
   check up on, clock out, collate, confirm, conform, conk,
   correspond, croak, cross-check, demonstrate, die, double-check,
   dovetail, drop, drop off, examine, fit in, gee,
   give an examination, go over, go west, harmonize, have it,
   have the qualifications, inspect, inventory, jibe, kick in,
   kick off, kick the bucket, knock off, look at, look over,
   measure up, monitor, observe, overhaul, overlook, pass, pass away,
   pass out, pass over, pass under review, peer at, peg out, peruse,
   pipe off, pop off, pore over, postmortem, prove, punch out,
   qualify, recheck, review, ring out, run over, scan, scrutinize,
   set an examination, shove off, sign out, size, size up, square,
   step off, study, survey, take stock, take stock of,
   take the measure, tally, test, triple-check, validate, verify