Strong’s Greek
G5400 — phobetron
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
φόβητρον φόβηθρον
phobetron — pronounced fob'-ay-tron
neuter of a derivative of 5399; a frightening thing, i.e. terrific portent:--fearful sight. see GREEK for 5399
1 occurrence in the KJV.
Luke 21:11
And great earthquakes shall be in divers places, and famines, and pestilences; and fearful sights and great signs shall there be from heaven.