A situation in which two suitors vie or compete for the love of the same person.

(mathematical analysis) The inequality that states that the magnitude of the sum of two vectors is less than or equal to the sum of the magnitudes of the vectors, or any equivalent inequality in other spaces.

(uranography) A bright asterism of the northern summer sky. Its corners are the three 1st-magnitude stars Altair (α Aql), Deneb (α Cyg), and Vega (α Lyr).

[the W- T-] (uranography) A bright asterism of the northern winter sky. Its corners are the three 1st-magnitude stars Betelgeuse (α Ori), Procyon (α CMi), and Sirius (α CMa).

(informal) One of several denominations of triangular postage stamps issued by the Cape of Good Hope during the period 1853-1864.

(mathematics) A geometric representation of the binomial coefficients in a triangle, each entry being the sum of the two entries above.

plural of Penrose triangle

(derogatory, dated) A Jehovah's Witness. / (historical) A Jehovah's Witness in Nazi Germany.

(slang) A homosexual.

(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.