Came across this today, and thought you all might also think the alternate spellings are interesting. I don't want to put the link because there are a couple of ads, but if anybody should happen to put the main term into The Free Dictionary, there is a good bit more information. Here's the relevant para.:

Tidal bore
The tidal bore in Upper Cook Inlet, AlaskaA tidal bore (or simply bore in context, or also aegir, eagre, or eygre) is a tidal phenomenon in which the leading edge of the incoming tide forms a wave (or waves) of water that travel up a river or narrow bay against the direction of the river or bay's current. As such, it is a true tidal wave and not to be confused with a tsunami, which is a large ocean wave traveling primarily on the open ocean.