IPA: /dɪˈfɛns.ləs/
KK: /dɪˈfɛns ləs/
Not having any protection or means to defend oneself; easily harmed or attacked.
The defenseless animals needed help to survive in the wild.
Defenseless → It is formed from "defens-" (from Latin "defendere", meaning to defend) and "-less" (meaning without). The word "defenseless" means without defense or protection.
Think of being 'without' ('-less') any 'defense' ('defens-') — that's why defenseless means unable to protect oneself.