(carpentry, construction) A plank or strip of wood, or several of such strips arranged side by side, used in construction to hold members of a structure together, to provide a fixing point, to strengthen, or to prevent warping.

(specifically) A strip of wood or metal used for various purposes, such as supporting lamps on a stage, protecting a ship's mast, holding down a tarpaulin, or closing the threads of a woof on a loom.

(intransitive) To batten is to improve in condition, become fertile, eat greedily, prosper at the expense of others, revel in, or gratify a morbid appetite or craving.

To furnish (something) with battens (noun sense 1).

(chiefly nautical) Chiefly followed by down: to fasten or secure (a hatch, opening, etc.) using battens (noun sense 2.2).