Meaning (4) is inaccurateEdit
I came here from wikipedia, so sorry if my style is incorrect. The definition for Noun (4) (Physics) may not be accurate. Other sources I've seen including Wikipedia define it more abstractly, without using the word "force" -- which has a specific technical meaning in physics. My interpretation would be something like: A region of space in which every point is, or can be, assigned the value of a physical entity such as: temperature (a "scalar field"); wind velocity or magnetic force ("vector fields"); or more abstract theoretical qualities such as potential energy.
The important thing is that it's not the "region affected by a force" that's important, but rather a specific quality of the region. Temperature, for example, is a field (every point in a region of space can be assigned a temperature) which isn't directly associated with a force.
field. (n.d.) The American Heritage® Dictionary of the English Language, Fourth Edition. (2003). Retrieved March 4 2007 from http://www.thefreedictionary.com/field