(geology) A geologic period within the Mesozoic era, comprising lower, middle and upper epochs from about 250 to 200 million years ago.

A three-pronged spear somewhat resembling a pitchfork. / (geometry) A curve of third order of the form:

(British spelling) A plane triangular graph on which are drawn all the colours that can be made by the additive mixing of red blue and green; these three primary colours are at the apices, while white is in the middle.

(American spelling) Alternative form of colour triangle

The area comprising the cities of Raleigh, Durham and Chapel Hill in North Carolina. Used with "the" except when attributive. / Ellipsis of Bermuda Triangle.

The process of finding a solution to a problem by trying many possible solutions and learning from mistakes until success is attained.

A (usually male) member of a tribe.

One who goes trick-or-treating on Halloween, usually a child dressed in a costume.

To extort small treats on Halloween by implied threat of property damage or practical joke.

(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.