Define "potentially hazardous food."

A potentially hazardous food is a natural or synthetic food that needs to be held at 41°F or colder or 135°F or hotter because it is in a form capable of supporting:

the rapid and progressive growth of infectious or toxigenic bacteria
the growth and toxin production of Clostridium botulinum or
in raw shell eggs, the growth of Salmonella Enteritidis

Potentially hazardous foods include foods of animal origin that are raw or heat-treated, a food of plant origin that is heat-treated or consists of raw seed sprouts, cut melons, and garlic-in-oil mixtures that have not been properly acidified to prevent the growth of pathogenic bacteria.

Potentially hazardous food does not include:

An air-cooled hard-boiled egg with shell intact, or a shell egg that is not hard-boiled, but has been treated to destroy all viable Salmonella, such as pasteurized in the shell eggs;
A food with a water activity value of 0.85 or less, such as jams or jellies;
A food with a pH level of 4.6 or below when measured at 75°F, such as properly prepared sushi rice or pickles;
A food, in an unopened hermetically sealed container, that is commercially processed to achieve and maintain commercial sterility under conditions of nonrefrigerated storage and distribution;
A food for which laboratory evidence demonstrates that the rapid and progressive growth of pathogens cannot occur.
A food that does not support the growth of pathogenic microorganisms even though the food may contain an infectious or toxigenic microorganism or chemical or physical contaminant at a level sufficient to cause illness.

SOURCE:
U.S. Food and Drug Administration. 2001. Food Code. The complete publication is available on-line at: http://www.fda.gov/food/foodsafety/retailfoodprotection/foodcode/foodcode2001/default.htm