2. To draw out or to remove as if by percolation or seepage; to dissolve, to remove, or to wash out: Francisca poured water through the ashes from the fireplace to leach the lye in the ash so she could make soap.
2. Someone who uses other people for personal gain or anyone who tries to get what he or she can swindle from others: Celebrities often have at least one leech who tries to leech them for money or other material rewards.
One species of the this blood-sucking worm has been used in medical treatments for many years to leech patients or to eat away putrid flesh from a wound.
When using a leech on the patient, the doctor was heard to comment that he wished it were as easy to leach toxins from the soil as it is to leech toxins from an ill person using a leech or two.
Is it proper to say that a leech can leach blood from an animal?
As a matter of fact, a leech is known to leech blood and dead flesh from bodies while leaching is quite a different process.
In chemical engineering, to leach is the procedure used for separating a soluble substance from a solid by washing or by the percolation of water or other liquid through the substance, as when making coffee.
In geochemistry, to leach is specifically the natural or artificial removal of soluble substances from rock, ore, or layers of soil by the action of percolating substances; such as, water.
A medicinal leech, known as Hirudo medicinalis was utilized in the distant past and is being used again in the modern application of leech blood from patients for specialized procedures.
There is also a tool being used by medical doctors called an artificial leech which consists of a cup and suction pump, or syringe, for drawing blood.
For much more information about leeches and leeching, go to this Medicine, Leeching for Health page.