* A regional term: It might be a local name for a specific type of boat or vessel used in a particular harbor.
* A nickname: Someone might have given a specific boat this nickname.
* A made-up term: It could be a fictional term from a book, movie, or game.
To understand what a "harbour dasher" is, I need more information.
Could you provide any context? For example:
* Where did you hear the term? (Specific location, book, etc.)
* What is the context of the term? (What was it being used to describe?)
With more information, I can help you figure out what a "harbour dasher" is!