The headword seems to be related to a series of words relating to orgiastic behavior and associated with the gods Dionysos and Pan ( LSJ entry at web address 1). Cf. Hesychius beta6, 9, 10 epsilon1287 (cf. Latte 1.501-2); Lexica Segueriana 223.31 Bekker; Photius Lexicon beta5, 6, 8; Etymologicum magnum 183.45. Its only appearance outside of lexicography is in the Doric vocative form βαβάκτα in a fragment of Kratinos (321 Kock, 22 Meineke, 359 Kassel-Austin), where it is an epithet of Pan. At Hesychius beta10 a possibly related word is identified as Lydian.
The gloss here is a word sparsely attested (two occurrences in an astrological work in a codex in Moscow: Catalogus Codicum Astrologorum Graecorum 12.178.17, 189.27), and in this case it seems likely to be a corruption of ὀρχηστής ('dancer') which appears in parallel entries in several other lexica (Hesychius beta6, L.S. 223.31 Bekker, Photios beta8), and which would have been nearly homophonous to ὀργιστής in late/Byzantine Greek. On the other hand, the meaning 'raging person' would not be foreign to the orgiastic context: μανιώδης ('maniacal') is also used as a gloss in the lexica cited above). Adler notes Suda MSS GIT and a corrector to MS V offer ὀρχηστής and related words as variant readings.