beelzebub(n = noun.person) devil, lucifer, old nick, prince of darkness, satan, the tempter - (Judeo-Christian and Islamic religions) chief spirit of evil and adversary of God; tempter of mankind; master of Hell;
is a kind of spiritual being, supernatural being

   The title of a heathen deity to whom the Jews ascribed the sovereignty of the evil spirits; hence, the Devil or a devil. See Baal. [1913 Webster]

beelzebub, n. the Devil.

Etymology:
OE f. L f. Gk beelzeboub & Heb. ba'al zeb{ucirc}b lord of the flies, name of a Philistine god

N  satan, the Devil, Lucifer, Mephistopheles, Ahriman, Belial, Samael, Zamiel, Beelzebub, the Prince of the Devils, the tempter, the evil one, the evil spirit, the Adversary, the archenemy, the author of evil, the wicked one, the old Serpent, the Prince of darkness, the Prince of this world, the Prince of the power of the air, the foul fiend, the arch fiend, the devil incarnate, the common enemy, the angel of the bottomless pit, Abaddon, Apollyon, fallen angels, unclean spirits, devils, the rulers, the powers of darkness, inhabitants of Pandemonium, demon, diabolism, devilism, devilship, diabolology, satanism, devil worship, manicheism, the cloven foot, satanic, diabolic, devilish, infernal, hellborn, Mythological and other fabulous Deities and Powers.