Onto or on a shore, reef, or the bottom of a body of water: a ship that ran aground; a ship aground offshore
When a boat is in water too shallow for it to float in, i e: the boat's bottom is resting on the ground
on a shore or reef; "a ship aground offshore"; "a boat aground on the beach waiting for the tide to lift it"
If a ship runs aground, it touches the ground in a shallow part of a river, lake, or the sea, and gets stuck. run/go aground if a ship runs aground, it becomes stuck in a place where the water is not deep enough
On the ground; stranded; a nautical term applied to a ship when its bottom lodges on the ground