συνεπιμαρτυρέωsynepimartyréō

to join in attesting, bear witness together with: Hebrews 2:4.

Greek (New Testament) · G4901

Same root

σύνsýn · G4862with or together (but much closer than G3326 (μετά) or G3844 (παρά)), i.e. by association, companionship, process, resemblance, possession, instrumentality, addition, etc.
ἐπιμαρτυρέωepimartyréō · G1957to attest further, i.e. corroborate

Where it appears

Appears 1 times in the Bible.

Hebrews 2:4 And God confirmed the message by giving signs and wonders and various miracles and gifts of the Holy Spirit whenever he chose.

Source: G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922), public domain.