To trawl means to search through something thoroughly and carefully, often requiring patience and effort. When you trawl through old photo albums looking for a specific picture, you examine each page methodically until you find what you need. A researcher might trawl through hundreds of documents to find important information for a project.

The word comes from a fishing method where boats drag large nets called trawls along the ocean floor, catching everything in their path. Commercial fishing vessels trawl the seas this way, though the method has become controversial because trawl nets can damage ocean habitats and catch unwanted marine life along with the fish people want to eat.

When used metaphorically, trawling suggests the same sweeping, comprehensive approach. A detective might trawl through security footage looking for clues, or a student might trawl the library shelves searching for books on ancient Egypt. The word implies you're casting a wide net, examining lots of material because you're not quite sure where you'll find what you're looking for. Unlike a quick search, trawling takes time and thoroughness.

As a noun, a trawl is the net used for this kind of fishing, or the act of fishing with it.