The Collaborative International Dictionary of English v.0.48:

Interlock \In`ter*lock"\, v. i.
   To unite, embrace, communicate with, or flow into, one
   another; to be connected in one system; to lock into one
   another; to interlace firmly.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Interlock \In`ter*lock"\, v. t.
   1. To unite by locking or linking together; to secure in
      place by mutual fastening.
      [1913 Webster]

            My lady with her fingers interlocked. --Tennyson.
      [1913 Webster]

   2. To connect together so that the parts work together as a
      coordinated unit; to connect as a single system.
      [PJC]

WordNet (r) 3.0 (2006):

interlock
    n 1: a device that prevents an automotive engine from starting;
         "car theives know how to bypass the ignition interlock"
         [syn: interlock, ignition interlock]
    2: the act of interlocking or meshing; "an interlocking of arms
       by the police held the crowd in check" [syn: mesh,
       meshing, interlock, interlocking]
    v 1: coordinate in such a way that all parts work together
         effectively [syn: interlock, mesh]
    2: hold in a locking position; "He locked his hands around her
       neck" [syn: lock, interlock, interlace]
    3: become engaged or intermeshed with one another; "They were
       locked in embrace" [syn: interlock, lock]

Moby Thesaurus II by Grady Ward, 1.0:

114 Moby Thesaurus words for "interlock":
   accord, aegis, agree, answer to, arm guard, assent, assort with,
   backstop, be consistent, be of one, be uniform with, buffer,
   bulwark, bumper, check, chime, cohere, coincide, concur, conform,
   conform with, consist with, contraceptive, cooperate, copyright,
   correspond, crash helmet, cushion, dashboard, dodger, dovetail,
   face mask, fall in together, fender, finger guard, fit together,
   foot guard, fuse, go together, go with, goggles, governor, guard,
   guardrail, hand guard, handrail, hang together, hard hat,
   harmonize, helmet, hit, hold together, insulation, interaffiliate,
   interally, interassociate, interconnect, intercouple, interdepend,
   interdigitate, interjoin, interlink, interrelate, intersect,
   intertie, jibe, knee guard, knuckle guard, laminated glass,
   life preserver, lifeline, lightning conductor, lightning rod, lock,
   mask, match, mudguard, nose guard, overlap, pad, padding,
   palladium, parallel, patent, pilot, preventive, prophylactic,
   protective clothing, protective umbrella, register, register with,
   respond to, safeguard, safety, safety glass, safety plug,
   safety rail, safety shoes, safety switch, safety valve, screen,
   seat belt, shield, shin guard, sing in chorus, sort with, square,
   square with, stand together, sun helmet, tally, umbrella,
   windscreen, windshield