WordNet (r) 3.0 (2006):

synapse
    n 1: the junction between two neurons (axon-to-dendrite) or
         between a neuron and a muscle; "nerve impulses cross a
         synapse through the action of neurotransmitters"

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "synapse":
   afferent neuron, autonomic nervous system, axon, brain,
   central nervous system, cerebral cortex,
   craniosacral nervous system, dendrite, effector organ,
   efferent neuron, ganglion, gray matter, internuncial neuron,
   medullary sheath, nerve, nerve trunk, nervous system, neuron,
   peripheral nervous system, plexus, sensorium, sensory area,
   sensory cell, solar plexus, spinal cord,
   thoracolumbar nervous system, white matter