Apollyon

Concise Bible Dictionary:

The Greek translation of the Hebrew name ABADDON, which signifies “destroyer.” He is king of the locusts of the bottomless pit, and ruler over the destroying agents that proceed from thence: it is one of the characters of Satan (Rev. 9:1111And they had a king over them, which is the angel of the bottomless pit, whose name in the Hebrew tongue is Abaddon, but in the Greek tongue hath his name Apollyon. (Revelation 9:11)).

Strong’s Dictionary of Greek Words:

Greek:
Ἀπολλύων
Transliteration:
Apolluon
Phonic:
ap-ol-loo’-ohn
Meaning:
active participle of 622; a destroyer (i.e. Satan)
KJV Usage:
Apollyon

Jackson’s Dictionary of Scripture Proper Names:

destroyer

Potts’ Bible Proper Names:

A destroyer, i. e., Satan:― "the angel of the bottomless pit" [ABADDON], Rev. 9:11. {Apollyon}