Weigh anchor is a nautical term indicating the final preparation of a sea vessel for getting underway.

Weighing anchor literally means raising the anchor

Anchor

An anchor is a device, normally made of metal, that is used to connect a vessel to the bed of a body of water to prevent the vessel from drifting due to wind or current. The word derives from Latin ancora, which itself comes from the Greek ἄγκυρα .Anchors can either be temporary or permanent...

 of the vessel from the sea floor and pulling it up to the side of the vessel after the engines have been brought up to operating power.

Example of use

USS Marvel (AM-262)

USS Marvel (AM-262)

USS Marvel was an built for the United States Navy during World War II. In 1945, she was transferred to the Soviet Navy under Lend-Lease as T-272. The Soviets converted her into a naval trawler in 1948 and renamed her Passat. She was stricken in 1964, never having been returned to U.S. custody....

's narrative is described in part in DANFS as "On 17 January 1945 she weighed anchor and began a 2-1/2-month cruise to Kodiak

Kodiak, Alaska

Kodiak is one of 7 communities and the main city on Kodiak Island, Kodiak Island Borough, in the U.S. state of Alaska. All commercial transportation between the entire island and the outside world goes through this city either via ferryboat or airline...

, Alaska

Alaska

Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

."

When not at anchor

When a vessel is not at anchor, but tied to a pier

Pier

A pier is a raised structure, including bridge and building supports and walkways, over water, typically supported by widely spread piles or pillars...

or to another anchored vessel, it does not weigh anchor; the captain or master gives the order to "Cast off lines!"