noun
pickled octopus
A food item: octopus that has been sliced and marinated in vinegar, often served as a side dish or drinking snack.
居酒屋で酢だこを注文した。
I ordered pickled octopus at the izakaya.
Compound of 酢 (su, 'vinegar') and 蛸 (tako, 'octopus'), with rendaku voicing of tako to dako.