plural of Penrose triangle

(idiomatic) A relationship involving three persons (usually two women and one man or two men and one woman) among whom there are conflicting and competing attachments of a romantic or emotional nature.

(graph theory) Of an undirected graph in which no three vertices form a triangle of edges.

A region of Thailand, Laos, Myanmar, famous for production of opium and heroin. / A region of Victoria, Australia, where the Victorian Gold Rush occurred.

(historical) A key communist Chinese and North Korean concentration area and communications junction during the Korean War, located in the central sector.

(US politics, political science) The policy-making relationship among the congressional committees, the bureaucracy (executive, sometimes called “government agencies”), and interest groups or lobbyists.

(geometry) A figure consisting of three circular arcs, each centered on the intersection of the other two.

A fractal consisting of three copies of itself, shrunk to half size, arranged in a triangular shape without rotating.

An optical illusion depicting an impossible solid object made of three straight beams of square cross section which meet pairwise at right angles at the vertices of the triangle they form.

(mathematics, engineering) A function or waveform that alternately ramps linearly upwards and then downwards.