Reading through this thread and seeing how many people read the title as "YOUR standard" and not "THE standard". Not sure if intention of thread?
When using a generic term for a Terrarian player character that's not an NPC-by-backstory, I usually just refer to them as "the local adventurer."
As illustrated by most other players here, there's a strong sense of player-surrogate going on. I can't really see there being any one 'default' Terrarian hero, as customization is included in-game right from the get-go of character creation. Sure there is a default when you first open it up, but how often do people stick to that when there are so many options just a few clicks away? Or just ONE click, if you're fine with hitting Random, which already makes a character more unique than a default warranting its own standalone name.
It's not like Minecraft Steve or Alex, where the character starts as a default and in order to change them you have to go and change an external source file to make the character your own, so the default would be more prevalent among those who don't realize that editing is an option (or couldn't be bothered to paint up their own skin).
*totally overthinking this. beeg sooprize*