Easton's Bible Dictionary (1897)
A modification of “Tertius;” a Roman advocate, whom the Jews employed to state their case against Paul in the presence of Felix (Acts 24:1-9). The charges he adduced against the apostle were, “First, that he created disturbances among the Romans throughout the empire, an offence against the Roman government (crimen majestatis). Secondly, that he was a ringleader of the sect of the Nazarenes; disturbed the Jews in the exercise of their
religion, guaranteed by the state; introduced new gods, a thing prohibited by the Romans. And thirdly, that he attempted to profane the temple, a crime which the Jews were permitted to punish.”
Smith's Bible Dictionary (1863)
(diminutive from Tertius), “a certain orator,” (Acts 24:1) who was retained by the high priest and Sanhedrin to accuse the apostle Paul at Caesarea before the Roman procurator Antonius Felix. He evidently belonged to the class of professional orators. We may infer that Tertullus was of Roman, or at all events of Italian, origin. (A.D. 55.)
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
TERTUL'LUS (diminutive of "Tertius"), a lawyer, probably a Roman, who, in consequence of their lack of familiarity with Roman forms of law, was hired by the Jews to act as prosecutor in the case of Paul before Felix. Acts 24:1-9.
Hitchcock's Bible Names (1869)
third