Other forms: battened down; battening down
To batten down is to prepare for a storm by securing anything that's loose. When sailors batten down the hatches, they fasten the covers that keep the cargo dry below the deck.
A batten is a strip of wood. Historically, sailors secured a hatch (a door to the space below deck) in a storm by nailing battens over tarps covering the hatch. This prevented flooding. Today, mariners still talk about battening down when they're getting ready for rough weather. So do coastal homeowners, who batten down before a hurricane by boarding up windows and bringing lawn chairs inside. Metaphorically, you can batten down in preparation for any difficulty: "Money's tight, but we'll batten down until business picks up."