|Noah Webster's Dictionary|
1. (a.) Not easily restrained; ungovernable; obstinate; stubborn.
2. (a.) Directed by ungovernable will, or proceeding from obstinacy.
Int. Standard Bible Encyclopedia
Headstrong (2 Occurrences)
2 Timothy 3:4 traitors, headstrong, conceited, lovers of pleasure rather than lovers of God; (WEB WEY ASV)
Titus 1:7 For the overseer must be free from all charge against him as God's steward; not headstrong, not passionate, not disorderly through wine, not a striker, not seeking gain by base means; (DBY)