Much of the confusion here is due to the different terminology and subtle differences in the way settings are applied between manufacturers.
The term trunk port or trunk connection is actually a Cisco term I believe but has come to be widely used to mean a link/port carrying tagged VLAN traffic, usually multiple VLANs but doesn't have to be.
I like to think of it like this, effectively there are three options for traffic on a VLAN leaving a switch port:
Tagged; the packet leaves the port with VLAN tags. Trunk port.
Untagged; the VLAN tags are stripped when the packet leaves the port. Access port. The PVID would almost always be set to that VLAN to re-tag the packets coming back in.
Excluded; packets from that VLAN are not permitted to leave via that port.
And indeed some switches mark the ports exactly like that which I always found the easiest to read. At least some HP switches are like that but lower end maybe...
It is better to avoid untagged and tagged traffic on the same link if you can. It's easy to make mistakes doing that. Some switches can behave unexpectedly. However it is valid.
The definitions between trunk port and access port blur when you have a port that is tagged on some VLANs but untagged on another.
They blur even further when you have multiple VLANs untagged on one port! Many (most?) switches won't allow that and it's of 'limited' use.

My own exposure to different switches is limited, open to thoughts on that.
Steve