| fanciful(adjective, strange, fantastic, doubtful, rare) |
| farcical(adjective, absurd) |
| faulty(adjective, poor, thin, false, small) |
| feeble |
| groundless(adjective, poor, irrational, unconvincing, unreasoned) |
| inadequate(adjective, poor, thin, false, shallow) |
| inane(adjective, poor, absurd, unconvincing) |
| ineffective(adjective, poor, inadequate, ineffectual, toothless) |
| ineffectual(adjective, poor, inadequate, ineffective, toothless) |
| marvelous(adjective, hard, amazing) |
| open to doubt(expression, idiom, extraordinary, amazing, incredible) |
| shaky(adjective, likely) |
| small(adjective, slight, poor, thin, inadequate) |
| specious(adjective, false, unreasonable, senseless, unpredictable) |
| strange(adjective, extraordinary, fantastic, doubtful, dubious) |
| stupid(adjective, absurd) |
| too much(expression, adjective, thin, informal, extraordinary) |
| trivial(poor, unconvincing) |
| unattainable(adjective, impossible) |
| unfeasible(adjective, impossible) |