From BiblePortal Wikipedia

Vine's Expository Dictionary of NT Words [1]

1: Ῥήτωρ (Strong'S #4489 — Noun Masculine — rhetor — hray'-tore )

from an obsolete present tense, rheo, "to say" (cp. Eng., "rhetoric"), denotes "a public speaker, an orator,"  Acts 24:1 , of Tertullus. Such a person, distinct from the professional lawyer, was hired, as a professional speaker, to make a skillful presentation of a case in court. His training was not legal but rhetorical.

Webster's Dictionary [2]

(1): ( n.) An officer who is the voice of the university upon all public occasions, who writes, reads, and records all letters of a public nature, presents, with an appropriate address, those persons on whom honorary degrees are to be conferred, and performs other like duties; - called also public orator.

(2): ( n.) In equity proceedings, one who prays for relief; a petitioner.

(3): ( n.) A plaintiff, or complainant, in a bill in chancery.

(4): ( n.) A public speaker; one who delivers an oration; especially, one distinguished for his skill and power as a public speaker; one who is eloquent.

King James Dictionary [3]

OR'ATOR, n. L.

1. A public speaker. In ancient Rome, orators were advocates for clients in the forum and before the senate and people. They were employed in causes of importance instead of the common patron. 2. In modern usage, a person who pronounces a discourse publicly on some special occasion, as on the celebration of some memorable event. 3. An eloquent public speaker a speaker, by way of eminence. We say, a man writes and reasons well, but is no orator. Lord Chatham was an orator. 4. In France, a speaker in debate in a legislative body. 5. In chancery, a petitioner. 6. An officer in the universities in England.

Fausset's Bible Dictionary [4]

(1)  Isaiah 3:3, "the eloquent orator"; rather as Vulgate, "skilled in whispering," i.e. incantation ( Psalms 58:5), Lachash .

(2) Tertullus, the Jewish accusers' advocate against Paul ( Acts 24:1). Paul as a Roman citizen was tried with Roman judicial forms ( Acts 25:9-10), the Roman lawyer pleading in Latin, as Norman French was formerly the language of law proceedings in England in Norman times.

Morrish Bible Dictionary [5]

1. lachash. This is joined with 'eloquent' in  Isaiah 3:3 , A.V., but signifies 'a whisper,' 'incantation,' and may be translated 'one versed in enchantments.' The R.V. has 'skilful enchanter.' See Divination

2. ῥήτωρ, 'a speaker.' At the trial of Paul before Felix, Tertullus was hired to argue their case, and plead for Paul's condemnation.  Acts 24:1 .

Hastings' Dictionary of the Bible [6]

Orator The term applied in   Acts 24:1 to Tertullus, who was the advocate for the high priest and elders against St. Paul. Men of this class were to be found in most of the provincial towns of the Roman Empire, ready to plead or defend any cause, and generally possessed of a certain amount of glib eloquence, with a due admixture of flattery.

Morley Stevenson.

Smith's Bible Dictionary [7]

Orator. The Authorized Version rendering in,  Isaiah 3:3, for what is literally, "Skillful In Whisper Or Incantation". The title is applied to Tertullus, who appeared as the advocate of the Jewish accusers of St. Paul before Felix,  Acts 24:1.

Hastings' Dictionary of the New Testament [8]

See Tertullus.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [9]

2. It stands for Ῥήτωρ , the title applied to Tertullus (q.v.), who appeared as the advocate or Patronus of the Jewish accusers of the apostle Paul before Felix ( Acts 24:1). The Latin language was used, and Roman forms observed in provincial judicial proceedings, as, to cite an obviously parallel case, Norman-French was for so many ages the language of English law proceedings. The trial of Paul at Caesarea was distinctly one of a Roman citizen; and thus the advocate spoke as a Roman lawyer, and probably in the Latin language (see  Acts 25:9-10; comp. Val. Max. 2:2, 2; Cicero, Pro Coelio, c. 30; Brutus, c. 37, 38,41, where the qualifications of an advocate are described; see Conybeare and Howson, Life and Epistles of St. Paul, 1:3; 2:348). (See Advocate).