Not in the IANA registry and not claimed by any well-known service.
There is no IANA assignment for 8481 on TCP or UDP, and Nmap lists it as "unknown" with an open rate around 0.015%. No mainstream software documents it as a default. If it is listening, the port was picked by whoever configured the host — the number itself carries no meaning you can look up.
Expose with care
Identify the listening process first. An unregistered port is not a safe port, it is an unlabelled one.
$ sudo lsof -nP -iTCP:8481 -sTCP:LISTENSeen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
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Corrections or a missing port? Reply @rimrocksystems.