Fetching details from the dictionary...
to buy in quantity; to buy a lot (of); to stock up (on); to lay in
台風の前に水や食料を買い込んだ。
I stocked up on water and food before the typhoon.
彼女は安売りのたびに必要以上に買い込んでいる。
She stocks up more than she needs every time there is a sale.
大切な食材を一度に大量に買い込む癖がある。
I have a habit of buying large amounts of important ingredients at once.