means The tiny junction between two nerve cells across which signals pass, usually by means of chemical messengers leaping the gap.

from Coined around the end of the 19th century by the physiologist Charles Sherrington, who needed a name for the nerve-cell junction; he reached back to the Greek synapsis, 'a clasping together' or 'junction,' built from syn- 'together' and haptein 'to fasten.' The story goes that a classicist colleague suggested the spelling, smoothing it from the harder-edged 'synaptein' to the word we now use.