Subject to, or causing doubt.
Experiencing or showing doubt, sceptical.
Improbable or unlikely.
Unclear or unreliable.
Suspicious, or of dubious character.
Undecided or of uncertain outcome.
A doubtful person or thing.
Provoking strife, controversy or discord.
One who makes specious arguments; one who is disputatious.
A type of dialogue or argument where the participants do not have any reasonable goal. The aim is to argue for the sake of conflict, and often to see who can yell the loudest.