1. A process to change (waste) materials into new products to prevent waste of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air pollution (from incineration) and water pollution (from landfilling) by reducing the need for “conventional” waste disposal, and lower greenhouse gas emissions as compared to plastic production. (wikipedia.org)
2. The collection and often reprocessing of discarded materials for reuse. Recycled materials include those used in manufacturing processes and those used in consumer products. The recycled material is often degraded somewhat by use or processing and therefore must be converted to another purpose. For example, the processing of recycled newspaper and other paper wastes usually shortens their fibers, and the material cannot be used to make high-grade paper. Instead, it can be reprocessed to make cardboard or insulation. Recycling helps reduce pollution, prolong the usefulness of landfills, and conserve natural resources. (thefreedictionary.com)
3. Recovery and reprocessing of waste materials for use in new products. The basic phases in recycling are the collection of waste materials, their processing or manufacture into new products, and the purchase of those products, which may then themselves be recycled. Typical materials that are recycled include iron and steel scrap, aluminum cans, glass bottles, paper, wood, and plastics. The materials reused in recycling serve as substitutes for raw materials obtained from such increasingly scarce natural resources as petroleum, natural gas, coal, mineral ores, and trees. Recycling can help reduce the quantities of solid waste deposited in landfills, which have become increasingly expensive. Recycling also reduces the pollution of air, water, and land resulting from waste disposal. (global.britannica.com)
4. The act of processing used or abandoned materials for use in creating new products (wordnetweb.princeton.edu)
Word origin: verbal noun from recycle (v.). Originally a technical term in oil-refining and similar industries.