A somewhat dated or literary term for a job or employment opportunity, often implying a hired position. In modern Japanese, 仕事 or 職 is more common.
He finally found a job.
Jobs are scarce due to the recession.
Compound of 雇い (yatoi, 'hiring') + 口 (kuchi, 'opening' or 'position'). The exact historical derivation is uncertain, but it likely originated as a term for a hired position or job opening.