The Collaborative International Dictionary of English v.0.48:

payload \pay"load`\ (p[=a]"l[=o]d`) n.
   The part of a missile or torpedo that carries the explosive
   charge.

   Syn: warhead, load.
        [WordNet 1.5]

   2. The goods carried by a large vehicle.

   Syn: cargo, lading, freight, load, loading, shipment,
        consignment.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

payload
    n 1: the front part of a guided missile or rocket or torpedo
         that carries the nuclear or explosive charge or the
         chemical or biological agents [syn: warhead, payload,
         load]
    2: goods carried by a large vehicle [syn: cargo, lading,
       freight, load, loading, payload, shipment,
       consignment]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "payload":
   atomic warhead, baggage, bird, blast, burden, cargo, carload,
   cartload, charge, consignment, freight, freightage, full load,
   goods, guided missile, haul, impedimenta, lading, load, luggage,
   missile, nuclear warhead, pack, rocket, shipload, shipment,
   thermonuclear warhead, torpedo, trailerload, trainload, truckload,
   vanload, war rocket, warhead