Entry also at Photius, Lexicon sigma700 Theodoridis (where the third glossing synonym, noh/sai poih/sw, has been corrupted to noh/sw. poih/sw). The headword is found in this sense in the Septuagint Psalms 31:8 (= KJV 32:8, "I will instruct thee and teach thee in the way which thou shalt go"), and is discussed in commentaries by Eusebius, Athanasius, and Theodoretus.
The verb is the future of sumbiba/zw, with contracted -a/w, as usual in Attic with verbs in -a/zw (cf. sigma 1367). Greek biba/zw 'cause to go' is the normal causative form of bai/nw 'go' and may thus be used to form a causative of any compound of bai/nw, here sumbai/nw.
In the Septuagint it translates three different Hebrew roots, all correctly translated in the KJV as 'teach': (1) ירה (teach), (2) דעה (knowledge; in the causative "to cause to know"), and (3) שכל (wisdom; in the causative "to make wise") (Exodus 4:12: והוריתיך , 15 והוריתי, 18.16והודעתי; Leviticus 10.11 ולהורת; Deuteronomy 4.9 והודעתם; Judges 13.8 ויורני; Psalms 31.8 ואורך; Isaiah 40.13 יודיענו, 14; Daniel 9.22 להשכילך). But the Greek verb adds implications not explicit in the Hebrew or English: that God, Moses or another teacher causes the student to join together ('go together' in the simplest sense of these verbs) with other worshippers in the same beliefs and ritual. See sigma 1367 above for an interesting verse by Paul in the NT (I Corinthians 2.16).
The odd definition by Hesychius appears based on the uses in the NT (for which see sigma 1367 and LSJ, web address 1). He defines the headword (sumbibw= se, sigma2291) incorrectly as a present tense: suna/ptw se, dida/skw se, sumporeu/omai se ('I fit you together, I teach you, I assemble you together', but the last verb should be intransitive!).
[1] This verb, usually 'establish', is apparently used as a causative of the verb e)pi/stamai 'know, know how to', used in philosophy of having e)pisth/mh. This use would be unparalleled; it may be better to take it from the idiom e)fi/sthmi to\n no/on ‘observe’ in the causative sense 'cause to observe'.