1. the voluntary or accidental dislodgment of aquatic invertebrates from the stream bottom into the water column where they move or float with the current 2. any detrital material transported by wind or water —see detritus 3. something washed ashore; a mass of water deposited ashore by wind or water currents —see dispersal 4. range management the natural movement of livestock as they graze or move toward water or bedding sites, etc. —see drive 5. the unintended movement of a pesticide by wind 6. soils sediments or rocks transported by glacial action 7. genetics the movement of plants or animals (genes) within or beyond their natural rangeThis definition last updated 10/25/2008