Digitalarkivet (the Digital Archives) of Norway has a wonderful dictionary online. It covers the years from 1300 to 1700. It is actually an old Danish dictionary, but that is the language that was used in Norway at that time.
Click on the following link, then choose a letter. The Norwegian/ Danish alphabet is as follows. A-Z, then Æ, Ø, Å. The last ones are vowels that follow after Z. After choosing a letter you will find many words starting with that letter. The words will not be translated to english, but many of the words you should be familiar with from searching early genealogical records: Early Danish/Norwegian Ordbok (Dictionary).
Another great book is: Store norske leksikon