Microsegmentation in computer networking is a term used to describe the segmentation

Network segmentation

Network segmentation in computer networking is the act or profession of splitting a computer network into subnetworks, each being a network segment or network layer...

 of a collision domain

Collision domain

A collision domain is a section of a network where data packets can collide with one another when being sent on a shared medium or through repeaters, in particular, when using early versions of Ethernet. A network collision occurs when more than one device attempts to send a packet on a network...

 into as many segments

Network segment

A network segment is a portion of a computer network. The nature and extent of a segment depends on the nature of the network and the device or devices used to interconnect end stations.-Ethernet:...

 as there are circuit

Telecommunication circuit

A telecommunication circuit is any line, conductor, or other conduit by which information is transmitted.A dedicated circuit, private circuit, or leased line is a line that is dedicated to only one use...

s, minus one (#segments = #circuits - 1). This microsegmentation performed by the switch

Network switch

A network switch or switching hub is a computer networking device that connects network segments.The term commonly refers to a multi-port network bridge that processes and routes data at the data link layer of the OSI model...

 cuts the collision domain down so that only two nodes coexist within each collision domain. This way, collisions are decreased and only the two network interface controllers which are directly connected via a point-to-point link are contending for the medium.