(1) Of, or relating to the transmitting end of a discharge across a synapse.
(2) Pertaining to or being situated at the proximal side of a synapse.
The term is used in physiology to refer to the transmitting or proximal side of a synapse, such as a presynaptic cell (e.g. a neuron) which releases neurotransmitters that bind with the receptors of a postsynaptic cell (e.g. a muscle cell, a gland cell or a neuron).
Word origin: pre- (before) + synaptic » synapse
See also: synapse