Capable of being alarmed or easily frightened; prone to experiencing alarm or fear.
From alarm (sudden fear or warning) plus the suffix -able (capable of), creating a descriptive term for someone who is easily startled or worried.
The word 'alarmable' appears mostly in old literature because it describes a personality trait that doctors used to treat seriously—they thought overly alarmable people had 'nervous dispositions' that needed special remedies.
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