defend

Concise Oxford English Dictionary © 2008 Oxford University Press:
defend/dɪˈfend/

▶verb

• 1 resist an attack on; protect from harm.

• 2 conduct the case for (the party being accused or sued) in a lawsuit.

• 3 attempt to justify.

• 4 compete to retain (a title or seat).

• 5 (in sport) protect one's goal or wicket rather than attempt to score against one's opponents.

– derivatives
defendable adjective,
defender noun.

– origin ME: from OFr. defendre, from L. defendere, from de- ‘off’ + -fendere ‘to strike’.