scavenge

from The American Heritage® Dictionary of the English Language, 5th Edition.

• intransitive verb To collect (useful items) by searching through refuse.
• intransitive verb To search through (a place or container) for useful items.
• intransitive verb To feed on (dead or decaying matter). Used especially of animals.
• intransitive verb To expel (exhaust gases) from a cylinder of an internal-combustion engine.
• intransitive verb To expel exhaust gases from (such a cylinder).
• intransitive verb To clean (molten metal) by chemically removing impurities.
• intransitive verb To remove or inactivate (harmful chemicals or impurities) in a mixture.
• intransitive verb To search through refuse for useful items.
• intransitive verb To feed on dead or decaying matter.

from The Century Dictionary.

• To cleanse from filth.
• In certain forms of the internal-combustion motor, to sweep out of (the cylinder) by an inrush of atmospheric air the burnt products of the previous combustion-stroke. By thus cleansing or scavenging the cylinder the fresh intake of combustible mixture is not diluted with incombustible gases, nor is it heated by them so as to contain less weight of fuel per cubic foot of volume.

from the GNU version of the Collaborative International Dictionary of English.

• intransitive verb (Internal-combustion Engines) To remove the burned gases from the cylinder after a working stroke.
• transitive verb To cleanse, as streets, from filth.
• transitive verb to salvage (usable items or material) from discarded or waste material.
• transitive verb To remove (burned gases) from the cylinder after a working stroke.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• verb transitive to collect and remove refuse, or to search through refuse for useful material
• verb transitive to remove unwanted material from something, especially to purify molten metal by removing impurities
• verb transitive to expel the exhaust gases from the cylinder of an internal combustion engine, and draw in air for the next cycle
• verb intransitive to feed on carrion or refuse

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb collect discarded or refused material
• verb remove unwanted substances from
• verb feed on carrion or refuse
• verb clean refuse from