Alkalinity - "The capacity of water for neutralizing an acid solution." - U.S. Geological Survey, 2010
Alaklinity - "Alkalinity is the acid neutralizing capacity of solutes in a water sample, reported in milliequivalents per liter. Alkalinity consists of the sum of titratable carbonate and noncarbonate chemical species in a filtered water sample." - Rounds, 2006
Alkalinity - "The capacity of a water to accept protons, i.e., hydrogen ions. It is usually expressed as milliequivalents per liter." - American Geological Institute, 1976
Alkalinity - "Alkalinity and acidity are then capacity factors that represent, respectively, the acid- and base-neutralizing capacities (ANC and BNC) of an aqueous system. For solutions that contain no protolysis system other than that of aqueous carbonate, alkalinity is a measure of the quantity of strong acid per liter required to attain a pH equal to that of a CT molar solution of Na2CO3....Thus alkalinity and acidity are convenient measures for estimating the maximum capacity of a natural base to neutralize acidic and caustic wastes without permitting extreme disturbance." - Stumm and Morgan, 1981
USGS - http://toxics.usgs.gov/definitions/alkalinity.html