Noun
An area of stagnant water and hot temperatures that acts as a breeding ground for disease vectors such as mosquitos.
(derogatory) A group of political extremists or an area that is dominated by them.
(derogatory) A set of extreme and crazy political positions.
Alternative form of fever swamp
Disease-ridden swamp.
Group of political extremists.
Extreme political positions.
Source: en.wiktionary.orgfever-swamp