Watson's Biblical & Theological Dictionary 
בתאּ?קול , daughter of the voice. By this name the Jewish writers distinguish what they called a revelation from God, after verbal prophecy had ceased in Israel; that is, after the prophets Haggai, Zechariah, and Malachi. The generality of their traditions and customs are founded on this Bath-Kol. They pretend that God revealed them to their elders, not by prophecy, but by the daughter of the voice. The Bath-Kol, as Dr. Prideaux shows, was a fantastical way of divination, invented by the Jews, like the Sortes Virgilianae [divination by the works of Virgil] among the Heathen. For, as with them, the words first opened upon in the works of that poet, was the oracle whereby they prognosticated those future events which they desired to be informed of; so with the Jews when they appealed to Bath- Kol, the next words which they should hear drop from any one's mouth were taken as the desired oracle. With some it is probable that Bath-Kol, the daughter of the voice, was only an elegant personification of tradition. Others, however, more bold, said that it was a voice from heaven, sometimes attended by a clap of thunder.
Charles Buck Theological Dictionary 
(i.e. the daughter of a voice, ) an oracle among the Jews, frequently mentioned in their books, especially the Talmud. It was a fantastical way of divination invented by the Jews, though called by them a revelation from God's will, which he made to his chosen people after all verbal prophesies had ceased in Israel.
Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
( בִּאּתאּקוֹל , Daughter f the Voice ) , a rabbinical name for a supposed oracular voice, which Jewish writers regard as inferior in authority to the direct revelation that the O.T. prophets enjoyed (Vitringa, Observ. Sacr. 2:338), although the Targum and Midrash affirm that it was the actual medium of divine communication to Abraham, Moses, David, Nebuchadnezzar, etc. (Reland, Ant. Sacr. pt. 2, ch. 9). Neither are the Jewish authorities agreed as to what the Bath-Kol itself was, many maintaining that it was merely the echo of the divine utterance (Buxtorf, Lex. Talm. s.v. בת ). Some scholars have incorrectly rendered the term "daughter-voice," daughter's voice (Horne, Introd. 4:149; Jennings, Jewish Antiq. bk. 1, ch. 6). It has been supposed that Josephus alludes to the Bath-Kol in the annunciation to Hyrcanus that his sons had conquered Antiochus (Ans. 13:10, 3), and the awful warning voice in the Temple prior to its destruction ( War, 5:5, 3); but these and other instances seem to fall short of the dignity required. Prideaux, however, classes them all with the heathen species of divination called Sortes Vigilanae (Connection, 2:354), and Lightfoot even considers them to be either Jewish fables or devices of the devil (Hor. Heb. ad Matthew 3:17). Yet instances of voices from heaven very analogous occur in the history of the early Christian Church, as that which was instrumental in making Alexander bishop of Jerusalem, and that which exhorted Polycarp to be of good courage (Eusebius, Hist. Ecclesiastes 6, l; 4:15). See Danz, De filia vocis (Jen. 1716; also in Meuschen's Nov. Test. ex Ta'mude illustr. p. 351-378); Haner, De הת קול (Jen. 1673); Metzler, De vocis filia (Jen. 1673). (See Word Of The Lord).