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1. A quality of water containing certain substances, esp. soluble salts of calcium and magnesium. These react with soaps, forming insoluble compounds that are precipitated out of solution, thus interfering with their cleansing action. 2. The quality or penetrating power of x-rays. Hardness increases as wavelengths become shorter. 3. The quality of firmness or density of a material imparted by the cohesion of the particles that compose it.

hardness test

A test designed to determine the relative hardness of materials by correlating the size or depth of an indent produced by a particular instrument with a known amount of compressive force. SEE: hardness number.

hard stop

In informatics and other forms of engineering, any mechanism that prevents further action once a critical threshold is reached.


A colloquial term for an implant, esp. an orthopedically placed nail, plate, rod, or screw.


Resourceful and resilient.


(hār′lĭp) [AS. hara, hare, + lippa, lip] Cleft lip.


Anything that impairs or adversely affects the safety of patients in clinical care, drug therapy, research investigations, or public health. Harms include adverse drug reactions, side effects of treatments, and other undesirable consequences of health care products and services.

harmful algal bloom

Red tide.

harmful drinking

Any level of alcohol consumption that results in physical, psychological, or social complications or injury; e.g., drinking during pregnancy.

Harmonia axyridis

(har-mōn′ē-ă ak-sir′ĭd-ĭs) The scientific name for a small multicolored beetle that may take up residence indoors, esp. during cooler weather. It is an important source of indoor allergies. It is found in the southern U.S. and in many other parts of the world. SYN: Asian lady beetle; multicolored Asian lady beetle.


In physics, concerning wave forms, an oscillation or frequency that is a whole number multiple of the basic frequency.


(har′mŏ-nē) [L. harmonia fr Gr. harmonia, framework, agreement] Agreement, balance, or compatibility.


(har′nĕs) In postamputation rehabilitation, the part of an upper extremity prosthesis that fits around the shoulder and back to permit mechanical control of the terminal device and hold the socket firmly around the stump.


(hăr-poon′) [Gr. harpazein, to seize] A device with a hook on one end for obtaining small pieces of tissue such as muscle for examination.

Harrison groove

(har′ĭ-sŏn) [Edwin Harrison, Brit. physician, 1779–1847] A ...

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