| fitful(doubtful, vague, hesitant, changeable, unsure) |
| forceless(adjective, void, meaningless, invalid, unsubstantiated) |
| fruitless(adjective, meaningless, invalid, unsubstantiated, unsupported) |
| groundless |
| hazardous(shaky, unlikely, unpromising) |
| hazy(doubtful, shaky, vague, hesitant, changeable) |
| iffy(uncertain, doubtful, unsettled, dubious, restricted) |
| impugnable(doubtful, shaky, risky, unlikely, unpromising) |
| incalculable(doubtful, vague, hesitant, changeable, unsure) |
| inconstant(doubtful, vague, hesitant, changeable, unsure) |
| indeterminate(uncertain, doubtful, vague, dubious, questionable) |
| indistinct(doubtful, shaky, vague, hesitant, changeable) |
| ineffective(adjective, meaningless, invalid, unsubstantiated, unsupported) |
| ineffectual(adjective, meaningless, invalid, unsubstantiated, unsupported) |
| inoperative(adjective, meaningless, invalid, unsubstantiated, unsupported) |
| insecure(doubtful, shaky, vague, unsure, unlikely) |
| irregular(doubtful, vague, hesitant, changeable, unsure) |
| irresolute(doubtful, vague, hesitant, changeable, unsure) |
| long shot(expression, doubtful, shaky, risky, unlikely) |
| makeshift |