The Collaborative International Dictionary of English v.0.48:

caesura \cae*su"ra\, n.; pl. E. caesuras, L. C[ae]sur[ae]
   [L. caesura a cutting off, a division, stop, fr. caedere,
   caesum, to cut off. See Concise.]
   A metrical break in a verse, occurring in the middle of a
   foot and commonly near the middle of the verse; a sense pause
   in the middle of a foot. Also, a long syllable on which the
   c[ae]sural accent rests, or which is used as a foot.
   [1913 Webster]

   Note: In the following line the c[ae]sura is between study
         and of.
         [1913 Webster]

               The prop | er stud | y of | mankind | is man.
         [1913 Webster]

   2. a pause or interruption (as in a conversation); as, after
      an ominous caesura the preacher continued.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

caesura
    n 1: a pause or interruption (as in a conversation); "after an
         ominous caesura the preacher continued"
    2: a break or pause (usually for sense) in the middle of a verse
       line

Moby Thesaurus II by Grady Ward, 1.0:

138 Moby Thesaurus words for "caesura":
   Alexandrine, abeyance, accent, accentuation, amphibrach,
   amphimacer, anacrusis, anapest, antispast, arsis, bacchius, beat,
   boundary, breach, break, cadence, catalexis, cease-fire, cessation,
   chloriamb, chloriambus, clearance, colon, comma, counterpoint,
   cretic, dactyl, dactylic hexameter, day off, diaeresis, dimeter,
   dipody, discontinuity, distance between, dochmiac, double space,
   drop, elegiac, elegiac couplet, elegiac pentameter, em space,
   emphasis, en space, epitrite, feminine caesura, fissure, foot,
   freeboard, gap, hair space, half space, heptameter, heptapody,
   heroic couplet, hesitation, hexameter, hexapody, hiatus, holiday,
   iamb, iambic, iambic pentameter, ictus, interim, interlude,
   intermediate space, intermezzo, intermission, intermittence,
   interruption, interspace, interstice, interval, ionic, jingle,
   jump, juncture, lacuna, lapse, layoff, leap, leeway, letup, lilt,
   lull, margin, masculine caesura, measure, meter, metrical accent,
   metrical foot, metrical group, metrical unit, metron, molossus,
   mora, movement, numbers, paeon, pause, pentameter, pentapody,
   period, point, proceleusmatic, pyrrhic, quantity, recess,
   remission, respite, rest, rhythm, room, semicolon, single space,
   space, space between, spondee, sprung rhythm, stand-down, stay,
   stop, stress, suspension, swing, syzygy, tetrameter, tetrapody,
   tetraseme, thesis, time interval, tribrach, trimeter, tripody,
   triseme, trochee, truce, vacation