A) A letter-number designator assigned to a geographic location
Grid locator is also known as grid square or more formally as a Maidenhead locator. A grid locator is a system for compressing both latitude and longitude into a short string of characters. On shortwave frequencies, positions are reported at square precision, and on VHF and UHF, subsquare precision is used.
The ARRL's W1AW station in Newington, Connecticut, is found in grid locator FN31.
The "grid square" is indicated by the first two letters and two numbers. Further precision can be specified by using the "subsquare" which is designated by the addition of two letters after the grid square, as FN44ig (W1AW's grid square with subsquare location).