The meaning of in Old Norse is a type of ship built for long sea voyages and it was used during the famous Viking expansion. Knarr was a vessel used for cargo storage, it was a cargo ship that had a wide hull and was deeper and shorten then the standard longship. The reason for this was for it to store more cargo and for much smaller crews to operate it.
The ship on average was around 16 meters and a beam of 5 meters. It could carry up to 24 tons and if compared to the cog the difference is huge. But it was mostly used to transport various goods like wool, timber, wheat, furs, etc. It was also used as a supply for food or support the warriors or traders that went on long expeditions. Various livestock was carried on these ships so it could be transported to the colonies of Iceland, Greenland and Vinland.
There are no archeological findings of the knarr, only one has been found so far in the channel in Roskilde Fjord in Denmark. It was among two warships and a ferryboat. There were five ships found total and they are displayed in the museum in Rosklide. There isn’t much information about this boat, but it was used by the vikings for a period of time even though it wasn’t that effective.
Greenhill, Basil (1976) Archaeology of the Boat