The Collaborative International Dictionary of English v.0.48:

Interstice \In*ter"stice\ (?; 277), n.; pl. Interstices. [L.
   interstitium a pause, interval; inter between + sistere to
   set, fr. stare to stand: cf. F. interstice. See Stand.]
   [1913 Webster]
   1. That which intervenes between one thing and another;
      especially, a space between things closely set, or between
      the parts which compose a body; a narrow chink; a crack; a
      crevice; a hole; an interval; as, the interstices of a
      wall.
      [1913 Webster]

   2. An interval of time; specifically (R. C. Ch.), in the
      plural, the intervals which the canon law requires between
      the reception of the various degrees of orders.
      [1913 Webster]

            Nonobservance of the interstices . . . is a sin.
                                                  --Addis &
                                                  Arnold.
      [1913 Webster]

WordNet (r) 3.0 (2006):

interstice
    n 1: a small structural space between tissues or parts of an
         organ; "the interstices of a network"
    2: small opening between things