Sudden surprise with fear or terror excited by apprehension of danger; in the military use, commonly, sudden apprehension of being attacked by surprise.
“It makes no sense in having a noisy alarm when your next-door neighbor cannot hear it, or when the only person who can hear the alarm is not always at home.”
“Maybe he would raise the alarm when John failed to show for his luncheon appointment.”
“Their cries became stained with alarm and horror at the departing children.”