tray  a flat-surfaced utensil for the conveyance of various objects or material. acrylic resin tray, an impression tray made of acrylic resin. impression tray, a horseshoe-shaped receptacle made of metal or other suitable material used to carry the impression material to the mouth, to confine the material in apposition to the surfaces to be recorded, and to control the impression material while it sets to form the impression.