[countable] [usually plural] the particular structures, weapons, and people that are used for protecting a place
Government forces have breached the rebels’ defences.
The city walls were built as a defence against invaders.
strengthen someone’s/something’s defences: He stressed the need to strengthen the nation’s defences.
flood defences (=structures built to prevent the sea or a river from coming into a place): New flood defences are being built along the river bank.
Synonyms and related words