The "Northwest Passage" was the term given by the USS Voyager crew to a relatively narrow region of Borg territory containing large numbers of quantum singularities, which was devoid of Borg activity.
In late 2373, the Voyager crew intended to traverse Borg space at the Northwest Passage to avoid engaging the Collective. However, they soon discovered that the region lacked Borg activity because the quantum singularities had been created by Species 8472 as entry points for their invasion of the galaxy from fluidic space. As Species 8472 were more powerful than the Borg and intended to annihilate all life in the galaxy, Captain Janeway decided to avoid the Passage and instead ally with the Borg to defeat Species 8472. (VOY: "Scorpion")
Background information Edit
Named after the Northwest Passage, a corridor through Canada linking the Pacific and Atlantic Oceans on Earth by passage near the Arctic Circle.