| ill-considered(adjective, careless, silly, foolish, trivial) |
| illogical |
| immature(careless, silly, stupid, thoughtless, impulsive) |
| impetuous(adjective, careless, bold, thoughtless, impulsive) |
| implausible(extraordinary, amazing, incredible) |
| impossible(extraordinary, silly, amazing, ridiculous, absurd) |
| impracticable(silly, foolish, fantastic, unwise, impractical) |
| impractical(silly, foolish, trivial, impulsive, half-baked) |
| improbable(extraordinary, amazing, incredible) |
| improvident |
| impulsive(careless, silly, crazy, thoughtless, unreliable) |
| inappropriate(silly, foolish, stupid, fantastic, absurd) |
| incogitable(extraordinary, amazing, dubious, astonishing, incredible) |
| inconceivable(extraordinary, amazing, incredible) |
| inconstant(adjective, careless, unstable, unreliable, changeable) |
| incredible(extraordinary, silly, amazing, ridiculous, absurd) |
| injudicious(weak, simple, careless, silly, foolish) |
| insuppressible(careless, thoughtless, impulsive, reckless, hasty) |
| jaunty |
| jumping to conclusions(expression, idiom, careless, thoughtless, impulsive) |