The best replacement for synapse is roubaix.

The best alternatives to synapse are rated as following:
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★★★  synaptic cleft
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★  flux rifle
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★  secteur
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★  chemical synapse
★  supersix
★  trek madone
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★  boltor prime
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★  defy
★  gnome do
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★  caad9
★  electrical synapse
★  caad 8
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  synaptic gap
  allez
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  neuromuscular junction
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Speaking about synapse, one probably shouldn't forget about neurons.

Other search terms related to synapse and their ratings are:
★★★★★ neurons
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