A boat, or a machine on a boat, whose job is to scoop mud, sand and stones off the bottom of a river, harbour or sea. Two reasons people do this: to keep a channel deep enough for ships to pass, since mud settles and slowly fills a waterway in; and to collect the sand and gravel itself for building. So a dredger is heavy working equipment, not a vehicle anyone rides for pleasure — you see them in ports, in river mouths, and along coasts where land is being reclaimed. Taiwan's west coast harbours use them constantly, and the sand-dredging vessels that show up in news reports about the Taiwan Strait are exactly this word. There is a second, much smaller dredger in the kitchen: a small container with holes in the lid for shaking flour or sugar over food. Same idea underneath — scooping and scattering — but the two meanings live in completely different worlds, and context always makes it obvious which one you have.

挖泥船、抽砂船（廚房那個小的叫「撒粉罐」）