| error-prone(adjective, unreliable, insecure, treacherous, incalculable) |
| fair-weather(adjective, unreliable, insecure, treacherous, incalculable) |
| fairweather(adjective, unreliable, insecure, treacherous, incalculable) |
| faithless(adjective, unreliable, insecure, treacherous, incalculable) |
| fallible(adjective, unreliable, insecure, treacherous, incalculable) |
| fast and loose(adjective, unreliable, insecure, treacherous, incalculable) |
| faulty(adjective, useless, unfit) |
| fly-by-night(adjective, unreliable, insecure, treacherous, incalculable) |
| fly by night(adjective, unreliable, insecure, treacherous, incalculable) |
| functionless |
| idealistic(wild, unreasonable, useless, absurd, abstract) |
| iffy(adjective, unreliable, insecure, treacherous, incalculable) |
| ill-suited(adjective, useless, unfit) |
| illogical(wild, unreasonable, useless, absurd, abstract) |
| impossible(adjective, wild, unreasonable, useless, absurd) |
| improbable(wild, unreasonable, useless, absurd, abstract) |
| improper(adjective, useless, unfit) |
| in disrepair |
| inadaptable(adjective, useless, unfit) |
| inane |