| impossible(adjective, wild, ridiculous, absurd, possible) |
| inconceivable(adjective, unreasonable, useless, absurd, hopeless) |
| unimaginable(adjective, unreasonable, useless, absurd, hopeless) |
| unthinkable(adjective, unusual, unreasonable, useless, ridiculous) |
| no-go(noun, adjective, wild, unreasonable, useless) |
| unworkable(adjective, possible, impossible, impracticable) |
| absurd(wild, unreasonable, useless, ridiculous, outrageous) |
| beyond belief(expression, absurd, unbelievable, implausible, preposterous) |
| improbable(wild, absurd, unbelievable, implausible, unrealistic) |
| incomprehensible(adjective, unlikely) |
| incredible(adjective, ridiculous, absurd, outrageous, unbelievable) |
| outlandish(ridiculous, absurd, outrageous, unbelievable, implausible) |
| preposterous(adjective, unreasonable, useless, ridiculous, absurd) |
| ridiculous(absurd, outrageous, unbelievable, implausible, preposterous) |
| unachievable(adjective, unreasonable, useless, absurd, hopeless) |
| unattainable(adjective, possible, impossible) |
| unbelievable(ridiculous, absurd, outrageous, implausible, improbable) |
| unfeasible(adjective, wild, unreasonable, useless, absurd) |
| unrealizable(adjective, possible, impossible) |
| far-fetched(absurd, unbelievable, implausible, preposterous, improbable) |