外がい側そく溝こうMeanings1nounlateral sulcus; Sylvian fissure; lateral fissureNeuroanatomical term for the deep groove separating the frontal and parietal lobes from the temporal lobe.外がい側そく溝こうは大だい脳のうの外がい側そく面めんにある深ふかい溝こうです。The lateral sulcus is a deep groove on the lateral surface of the cerebrum.