|Noah Webster's Dictionary|
1. (a.) Not settled in opinion; undetermined; wavering; hesitating in belief; also used, metaphorically, of the body when its action is affected by such a state of mind; as, we are doubtful of a fact, or of the propriety of a measure.
2. (a.) Admitting of doubt; not obvious, clear, or certain; questionable; not decided; not easy to be defined, classed, or named; as, a doubtful case, hue, claim, title, species, and the like.
3. (a.) Characterized by ambiguity; dubious; as, a doubtful expression; a doubtful phrase.
4. (a.) of uncertain issue or event.
5. (a.) Fearful; apprehensive; suspicious.
Doubtful (4 Occurrences)
Matthew 28:17 And when they saw him they gave him worship: but some were in doubt. (See NAS)
Luke 12:29 And seek not ye what ye shall eat, or what ye shall drink, neither be ye of doubtful mind. (KJV ASV WBS)
Romans 14:1 Him that is weak in the faith receive ye, but not to doubtful disputations. (KJV WBS)
2 Corinthians 13:7 And our prayer to God is that you may do nothing wrong; not in order that our sincerity may be demonstrated, but that you may do what is right, even though our sincerity may seem to be doubtful. (WEY)