of pack-the act or process of one who packs.-any material used to pack, fill up, or make close.-a substance or piece used to make a joint impervious-a thin layer, or sheet, of yielding or elastic material inserted between the surfaces of a flange joint.-the substance in a stuffing box, through which a piston rod slides.-a yielding ring, as of metal, which surrounds a piston and maintains a tight fit, as inside a cylinder, etc.-same as filling.-a trick; collusion.