Final answer:
An ad hoc network is a type of wireless network where client devices directly communicate with each other without an Access Point. Mesh networks, star networks, and ring networks have different topologies and are not characterized by peer-to-peer communications without a central controller.
Step-by-step explanation:
A wireless networking topology in which client devices communicate directly with each other without the use of a controlling Access Point (AP) is called an Ad hoc network. This type of network is often formed spontaneously and does not require a predefined infrastructure, making it suitable for peer-to-peer (P2P) communications and quick, temporary network set-ups.
Mesh networks are characterized by each node connecting to multiple other nodes, creating a network structure that can dynamically re-route around any node that drops out.
Star networks have each client device connected to a central node, typically an access point or a switch, from which all communication passes through.
Lastly, Ring networks connect devices in a closed loop, with each device only having two connections, one on either side. While ring networks are rare today, they were once commonly used for local area networks (LANs).