Definition: Pockets are considered difficult targets, or "tight", when they frequently reject shots not made with enough precision. The pockets may become tightened via trimming the felt a certain way and/or reshaping the entry and sides of the openings of the pockets to reject imprecise shots or simply providing smaller than normal pocket openings.
A worn pocket can become loose, or if the plating on its back rejects too fast a shot, "tight". A poor table, therefore, might have six pockets with six different degrees of "tightness". Good players adjust to shoot a bit faster or slower, etc., when pockets need repair.
Examples:
Jimmy the French loved challenging all comers on "his" table for its tight pockets.
