Definition of marginalism in US English:

marginalism

noun

Economics
  • A form of economic analysis which argues that the economic value of a product is determined by the price or rate of exchange of the last unit supplied on the market.

Origin

Early 20th century; earliest use found in Journal of Political Economy. From marginal + -ism.

Pronunciation

marginalism

/ˈmɑːdʒɪnəlɪz(ə)m/