Definition of understaff in US English:

understaff

verb

[with object]usually as adjective understaffed
  • Provide with too few staff members to operate effectively.

    ‘the department is understaffed and overworked’
    ‘an understaffed hospital’
    ‘the security company was found to have routinely understaffed the facility’

Pronunciation

understaff

/ˌəndərˈstæf//ˌəndərˈstaf/