Debris (pronounced dayBREE) is a word used to describe the remains of something that has been otherwise destroyed.

Depending on context, debris can refer to a number of different things:

• In cosmology, debris usually refers to the remains of spacecraft that have either fallen to Earth or are still orbiting Earth, and is generally known as space debris. Space debris may also consist of natural components such as chunks of rock and ice. The problem of space debris has grown as various space programs have left legacies of launches, explosions, repairs, and discards in both low Earth orbit and more remote orbits. These orbiting fragments have reached a great enough proportion as to constitute a hazard to future space launches of both satellite and manned vehicles. Various government agencies and international organizations are beginning to track space debris and also research possible solutions to the problem. While many of these debris items, ranging in size from nuts and bolts to entire satellites and spacecraft, may fall to Earth, other items located in more remote orbits may stay aloft for centuries. The velocity of some of these pieces of space junk have been clocked in excess of 17,000 miles per hour. A piece of space debris falling to Earth leaves a fiery trail, just like a meteor.

• In marine environments, debris usually applies to floating garbage such as bottles, cans, styrofoam, cruise ship waste, offshore oil and gas exploration and production facilities pollution, and fishing paraphanalia from professional and recreational boaters. Marine debris is also called litter. It can enter the water directly through dumping into bodies of water or indirectly through runoff via rivers and streams. Marine debris threatens both marine life and coastal human habitations. The Beaches Environmental Assessment and Coastal Health Act (BEACH) of 2000 was enacted to help reduce the risk of diseases for users of the Nation's coastal waters. The act authorizes the EPA to award program development and implementation grants to eligible states, territories, tribes, and local governments to support microbiological testing and monitoring of coastal recreational waters, including the Great Lakes, that are adjacent to beaches or similar points of access used by the public. Other legislative initiatives and activities are underway to reduce this form of pollution as well.

• In geology, debris usually applies to the remains of geological activity including landslides, volcanic explosions, avalanches, mudflows, and lava eruptions. Geological debris sometimes moves in a stream called a debris flow. Debris flows are often referred to as mudslides, mudflows, or debris avalanches. They consist primarily of geological material mixed with water. The composition of this type of flow is mainly soil and other matter, such as trees and rock fragments, that are picked up as the flow moves down a slope or channel. Debris flows may be generated when hillside colluvium or landslide material becomes rapidly saturated with water and flows into a channel. Heavy rainfall, snowmelt, or high levels of ground water flowing through cracked bedrock may trigger a movement of this type. Debris flows and floods may also occur when strong rains on hill or mountain slopes cause extensive erosion and/or what is known as "channel scour". Debris flows can be as thick as wet mud mixed with rock, and can transport very large boulders. Debris flows may also eventually become thinner muddy flood waters as they deposit their heavier components. Geological debris flows tend to move in pulses as friction or other barriers are overcome during the flow. Sometimes earlier pulses or previous debris flows form levees that channel the flow until they are breached. The presence of older levees indicates the recurrence and characteristics of debris flows in a particular area. This can be important information for developing land on what are known as "alluvial fans".

• In medicine, debris usually refers to biological matter that has accumulated or lodged in surgical instruments and is referred to as surgical debris. The presence of surgical debris can result in cross-infections or nosocomial infections if not removed and the affected surgical instruments or equipment properly disinfected.

• In meteorology, debris usually applies to the remains of human habitation and natural flora after storm related destruction.

• In a general sense, the term debris is used to refer to man-made garbage.