The Collaborative International Dictionary of English v.0.48:

Nero \Ne"ro\ (n[=e]"r[-o]), prop. n.
   A Roman emperor notorious for debauchery and barbarous
   cruelty; hence, any profligate and cruel ruler or merciless
   tyrant. -- Ne*ro"ni*an (n[-e]*r[=o]"n[i^]*an), a.
   [1913 Webster] Nero (originally Lucius Domitius Ahenobarbus,
   later Nero Claudius Caesar Drusus Germanicus). Born at
   Antium, Italy, Dec. 15, 37 a. d.: committed suicide near
   Rome, June 9, 68. Roman emperor 54-68, son of Domitius
   Ahenobarbus and Agrippina (daughter of Germanicus).
   He was adopted by his stepfather, the emperor Claudius, in
   50, and in 53 married Octavia, the daughter of Claudius by
   Messalina. In 54 Claudius was poisoned by Agrippina, who
   caused her son to be proclaimed to the exclusion of
   Britannicus, the son of Claudius. His former tutors, the
   philosopher Seneca and Burrus, commander of the pretorian
   guards, were placed at the head of the government, and the
   early years of his reign were marked, on the whole, by
   clemency and justice. He caused his rival Britannicus to be
   removed by poison in 55. In 59 he procured the assassination
   of his mother, of whose control he had become impatient.
   Burrus died in 62, whereupon Seneca retired from public life.
   Freed from the restraint of his former advisers, he gave free
   rein to a naturally tyrannical and cruel disposition. He
   divorced Octavia in order to marry Poppaea, and shortly
   afterward put Octavia to death (62). Poppaea ultimately died
   from the effects of a kick administered by her brutal
   husband. Having been accused of kindling the fire which in 64
   destroyed a large part of Rome, he sought to divert attention
   from himself by ordering a persecution of the Christians,
   whom he accused of having caused the Conflagration. He put
   Seneca to death in 65, and 66-68 visited Greece, where he
   competed for the prizes as a musician and charioteer in the
   religious festivals. He was overthrown by a revolt under
   Galba, and stabbed himself to death with the assistance of
   his secretary.
   But the imperial Reign of Terror was limited to a
   comparatively small number of families in Rome. The provinces
   ware undoubtedly better governed than in the later days of
   the Republic, and even in Rome itself the common people
   strewed flowers on the grave of Nero.
   --Hodgkin, Italy and her Invaders, I. 6.
   [Century Dict. 1906]

WordNet (r) 3.0 (2006):

Nero
    n 1: Roman Emperor notorious for his monstrous vice and
         fantastic luxury (was said to have started a fire that
         destroyed much of Rome in 64) but the Roman Empire remained
         prosperous during his rule (37-68) [syn: Nero, Nero
         Claudius Caesar Drusus Germanicus, Lucius Domitius
         Ahenobarbus]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

NERO
       Neuro-Evolving Robotic Operatives [project]


Easton's 1897 Bible Dictionary:

Nero
   occurs only in the superscription (which is probably spurious,
   and is altogether omitted in the R.V.) to the Second Epistle to
   Timothy. He became emperor of Rome when he was about seventeen
   years of age (A.D. 54), and soon began to exhibit the character
   of a cruel tyrant and heathen debauchee. In May A.D. 64, a
   terrible conflagration broke out in Rome, which raged for six
   days and seven nights, and totally destroyed a great part of the
   city. The guilt of this fire was attached to him at the time,
   and the general verdict of history accuses him of the crime.
   "Hence, to suppress the rumour," says Tacitus (Annals, xv. 44),
   "he falsely charged with the guilt, and punished with the most
   exquisite tortures, the persons commonly called Christians, who
   are hated for their enormities. Christus, the founder of that
   name, was put to death as a criminal by Pontius Pilate,
   procurator of Judea, in the reign of Tiberius; but the
   pernicious superstition, repressed for a time, broke out again,
   not only throughout Judea, where the mischief originated, but
   through the city of Rome also, whither all things horrible and
   disgraceful flow, from all quarters, as to a common receptacle,
   and where they are encouraged. Accordingly, first three were
   seized, who confessed they were Christians. Next, on their
   information, a vast multitude were convicted, not so much on the
   charge of burning the city as of hating the human race. And in
   their deaths they were also made the subjects of sport; for they
   were covered with the hides of wild beasts and worried to death
   by dogs, or nailed to crosses, or set fire to, and, when day
   declined, burned to serve for nocturnal lights. Nero offered his
   own gardens for that spectacle, and exhibited a Circensian game,
   indiscriminately mingling with the common people in the habit of
   a charioteer, or else standing in his chariot; whence a feeling
   of compassion arose toward the sufferers, though guilty and
   deserving to be made examples of by capital punishment, because
   they seemed not to be cut off for the public good, but victims
   to the ferocity of one man." Another Roman historian, Suetonius
   (Nero, xvi.), says of him: "He likewise inflicted punishments on
   the Christians, a sort of people who hold a new and impious
   superstition" (Forbes's Footsteps of St. Paul, p. 60).

     Nero was the emperor before whom Paul was brought on his first
   imprisonment at Rome, and the apostle is supposed to have
   suffered martyrdom during this persecution. He is repeatedly
   alluded to in Scripture (Acts 25:11; Phil. 1:12, 13; 4:22). He
   died A.D. 68.