| faltering(weak, unstable, unsettled, unsteady, trembling) |
| fluctuates |
| fluctuating |
| fly-by-night(adjective, uncertain, nervous, doubtful, shaky) |
| frail(unstable, vulnerable, dangerous, unprotected, precarious) |
| harmonic |
| hazardous(unstable, vulnerable, risky, dangerous, unprotected) |
| hesitant(adjective, uncertain, nervous, unstable, doubtful) |
| idiosyncratic(irregular, unpredictable, unreliable) |
| immature(unstable, vulnerable, dangerous, unprotected, precarious) |
| in a quandary(expression, adjective, idiom, uncertain, nervous) |
| inconsistent(irregular, unpredictable, unreliable) |
| inconstant(adjective, irregular, unpredictable, unreliable) |
| indecisive(adjective, uncertain, nervous, unstable, doubtful) |
| indeterminate(adjective, uncertain, nervous, doubtful, shaky) |
| infirm(adjective, weak, unstable, unsettled, unsteady) |
| insubstantial(unstable, vulnerable, dangerous, unprotected, precarious) |
| irresolute(adjective, uncertain, nervous, unstable, doubtful) |
| jellylike(weak, unstable, unsettled, shaky, unsteady) |
| jerry-built(weak, unstable, unsettled, unsteady, trembling) |