from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Situated in front of or occurring before a synapse: a presynaptic nerve fiber; a presynaptic stimulus.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. in a synapse, of or pertaining to the neuron that releases neurotransmitter into the synaptic cleft
pre- + synaptic (Wiktionary)