| error-prone(adjective, unreliable, insecure, treacherous, incalculable) |
| excitable(adjective, passionate, excited, unstable, unpredictable) |
| explosive(adjective, passionate, uncertain, unstable, unpredictable) |
| faddish |
| fairweather(adjective, unreliable, insecure, treacherous, incalculable) |
| faltering(adjective, unfaithful, disloyal) |
| far-fetched(uncertain, doubtful, unsure) |
| fiery(adjective, passionate, unstable, unpredictable, unreliable) |
| fishy(uncertain, doubtful, unsure) |
| flaccid(adjective, uncertain, feeble, shaky, hesitant) |
| flirtatious |
| fluctuant(adjective, uncertain, nervous, unstable, doubtful) |
| fly by night(adjective, unreliable, insecure, treacherous, incalculable) |
| forceless(adjective, uncertain, feeble, shaky, hesitant) |
| foxy |
| freakish |
| froward(adjective, passionate, unstable, unpredictable, unreliable) |
| halfhearted(adjective, irresolute) |
| harebrained(careless, excited, immoral, thoughtless, unreliable) |
| headstrong(adjective, passionate, unstable, unpredictable, unreliable) |