defenceless

adjective

1 it is a disgrace that these thugs terrorized defenceless animals:

vulnerable, helpless, powerless, impotent, weak, frail;

susceptible, easily hurt/wounded/damaged;

rare impuissant, resistless.

▷antonyms well protected, resilient.

2 scrapping the weapons would leave the country wholly defenceless:

undefended, unprotected, unguarded, unfortified, unshielded, unarmed, without arms, without defences;

vulnerable, assailable, open to attack, wide open, open, exposed, endangered, in danger, in peril, in jeopardy, at risk, insecure;

rare pregnable.

▷antonyms well protected.

defenceless Oxford Dictionary of English