(1)
To pinch a boat is to sail her so close to the wind that the sails lose their
drive, even though they are still drawing. One may say ‘You’re pinching her’,
or simply, ‘You’re pinching’. (See Starve.)

Pinch, to (2)
A hull which has been slightly crushed or squeezed is said to have been pinched. When buying a second-hand boat, one must look out for distortion
resulting from pinching – which is not so unlikely as it may sound, since a
small boat may easily find herself berthed between two bigger ones. (See also: Hogged)

Pinch, to (3) A yacht with pinched ends is usually one that was designed to the IOR handicapping rule as it stood in the ’70s. A pinched stern may have given a racing yacht of that vintage a good rating – but they rolled down-wind. Basically a wide beam and narrow at the ends.