A northwester is a strong wind, or a storm, coming from the northwest. Weather words name a wind by where it starts, not where it is going, so a northwester blows out of the northwest and pushes towards the southeast. You mostly meet it in weather reports, on boats, and in older books. Everyday talk more often says a northwest wind or a northwesterly. Though actually, in some coastal places the northwester is not just any breeze from that side — it is a known local wind, often hard or stormy, that people there treat as a kind of weather with its own name. It is not a common classroom word; when you see it, think northwest plus a strong wind.