One of the mysteries of the English language finally explained.
Definition of supermarginal in English:
supermarginal
adjective
1Zoology and Anatomy= supramarginal.
2Better or more than marginal in quality or degree; (Economics) involving or achieving a greater than marginal level of profit or value.
3Economics. Of land or ore: of greater profitability than marginal land or ore. Of a farmer, etc.: working such land.
4Politics. Designating a constituency, etc., in which an election is expected to be extremely closely contested, the sitting or outgoing member typically having only a very small majority.
noun
1Zoology. A supermarginal part; especially one of the plates lying above the marginal plates of a starfish arm. rare.
2Politics. A supermarginal constituency or seat.
Origin
Mid 19th century; earliest use found in James Dana (1813–1895), geologist, zoologist, and teacher. From super- + marginal.