The sad truth is, people interpret it any way they like to mean "things that make them feel icky". To some, a church that moves to be compassionate to gays or muslims are led by false prophets. To some, to teach infant baptism or "saved at birth" is the sign of a false prophet.
There are guidelines, specifically, "do not deny Christ" as "do not hold any other as Christ", and "do not add to scripture" (which is definitely different than do not interpret scripture, but rather to not contribute words to scripture and say they are holy), "do not hold oneself as authority over God". There are others, but these are probably the chief indicators of "false prophets".