unguardableadj.
Etymology: Previous versions of the OED give the stress as: unˈguardable.
the world > action or operation > harm or detriment > danger > [adjective] > exposed to danger > vulnerable > unguarded > unable to be guarded
1690 14 Yet this boldly asserted impregnable Fortress hath an unguardable Breach.
This entry has not yet been fully updated (first published 1924; most recently modified version published online June 2019).