noun

• (fishing) A net dragged across the bottom of a body of water.
  "Anchovy dragnets are an important part Korea's fishing sector. Over 99% of catches found in anchovy dragnets are anchovy. Although the annual total catches of anchovy have fluctuated, dragnets catch 55 to 70% of the total annual catch of anchovy. The remaining portion is caught with drift gill nets (10%) and other fishing methods."
• (law enforcement) Heightened efforts by law enforcement personnel undertaken in order to capture suspects.
  "The use of algorithms in policing is one example of their increasing influence on our lives.[…]who, if anyone, is policing their use[?] Such concerns were sharpened further by the continuing revelations about how the US National Security Agency (NSA) has been using algorithms to help it interpret the colossal amounts of data it has collected from its covert dragnet of international telecommunications."

verb

• (fishing, transitive) To drag a net across the bottom of a body of water.
  "When ponds are cleaned out periodically, fish are trapped or dragnetted and finally the pond is drained to remove all fish."
• (law enforcement, transitive) To undertake heightened efforts to catch a suspect.
  "In fact, Carty was not the man, but, after a police swoop had dragnetted twenty men suspected of having taken part in the business, he was lodged in Sligo jail and accused of this violence to the lady."