The Collaborative International Dictionary
Porism \Po"rism\, n. [Gr. ? a thing procured, a deduction from a demonstration, fr. ? to bring, provide: cf. F. porisme.]
(Geom.) A proposition affirming the possibility of finding such conditions as will render a certain determinate problem indeterminate or capable of innumerable solutions.
(Gr. Geom.) A corollary.
--Brande & C.
Note: Three books of porisms of Euclid have been lost, but several attempts to determine the nature of these propositions and to restore them have been made by modern geometers.
n. 1 (context geometry English) A proposition affirming the possibility of finding such conditions as will render a certain determinate problem indeterminate or capable of innumerable solutions. 2 A corollary.
A porism is a mathematical proposition or corollary. In particular, the term porism has been used to refer to a direct result of a proof, analogous to how a corollary refers to a direct result of a theorem. In modern usage, a porism is a relation that holds for an infinite range of values but only if a certain condition is assumed, for example Steiner's porism. The term originates from three books of Euclid with porism, that have been lost. Note that a proposition may not have been proven, so a porism may not be a theorem, or for that matter, it may not be true.
Usage examples of "porism".
It is not quite clear what a porism was to Euclid but from later commentators it appears to have been a conception intermediate between a theorem and a problem.