noun
bum; slacker; good-for-nothing; loser
A derogatory term for a person who lacks motivation, energy, or willingness to work; often used in casual, critical contexts.
あいつは本当にずくなしだな。
That guy is a real slacker.
ずくなしの弟に仕事を探すように言った。
I told my good-for-nothing younger brother to look for a job.
怠け者 is a more standard word for a lazy person, while ずくなし is more colloquial and carries a stronger nuance of being utterly useless or unmotivated.
Derived from ずく (motivation, energy) + 無し (without). The exact origin of ずく is uncertain, but it is a dialectal or colloquial term for drive or initiative.