(architecture) The iron hook fixed to a casement to pull it shut, or to hold it partly open at a fixed point.
(finance) A reduction in the price of a financial instrument after reaching a peak
(differential geometry) The map between cotangent bundles of manifolds corresponding to a smooth map between smooth manifolds, which at each point is the dual map to the corresponding pushforward.
(category theory) The limit of a corner of arrows, which is a pair of arrows sharing the same codomain.
