Main Entry: pre·syn·ap·tic Pronunciation: -s&-'nap-tik Function: adjective : relating to, occurring in, or being part of a nervecell by which a wave of excitation is conveyed to a synapse <presynaptic terminals> <presynaptic inhibition> presynaptic membrane> —pre·syn·ap·ti·cal·ly/-ti-k(&-)lE/adverb