IPA: /ˌʌndərˈmænd/
KK: /ʌndərˈmænd/
Having fewer people than needed to perform a task or job effectively.
The project was delayed because the team was undermanned and couldn't meet the deadlines.
Undermanned → It is formed from "under-" (meaning below or insufficient) and "manned" (from the verb "man" meaning to staff or provide with personnel). The word "undermanned" means having insufficient personnel or being below the required number of staff.
Think of being 'below' ('under-') the needed number of people to 'staff' ('man') a task — that's what undermanned means.