noun
sail with the wind at its back
Nautical term for a sail that is filled from behind, pushing the boat forward.
追い風を受けて裏帆の状態で進む。
We sail with the wind at our back, the sail filled from behind.
adverb
aback
Adverbial use describing a sail pressed back against the mast by a headwind, often unintentionally.
突然の向かい風で帆が裏帆になった。
The sail was taken aback by a sudden headwind.