(geometry) A triangle one of whose angles is obtuse.

(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).

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

[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).

plural of Cape triangle

(by extension) Any place where things mysteriously disappear.

An area in the Atlantic Ocean where many ships and planes have disappeared under allegedly mysterious circumstances.

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

plural of Calot's triangle

Used other than figuratively or idiomatically: see black, triangle. / (ufology) One of a class of triangle-shaped unidentified flying objects, usually with a light in each corner.