Meaning – The term inbound, refers to the signal or data that is being received by the system or the network. There is a lot of data and signals that are transmitted and received on a daily basis. When a computer sends a bit of data or a signal to another system, then the signal that is about to be received by the recipient is termed as the inbound data or inbound signal.
In the context of firewalls, the term inbound refers to inbound rules. These are to do with other things accessing your computer. If you are running a Web Server on your computer then you will have to tell the Firewall that outsiders are allowed to connect to it.
Example of usage – “When the employee requested his colleagues to send him the mission-critical data, he received a notification on his computer that there was an incoming package carrying the data elements.”