| erratic(adjective, random, haphazard) |
| faded(adjective, weak, pale) |
| failing(verb, adjective, weak, delicate, ill) |
| faulty(adjective, weak, feeble) |
| flickering |
| flimsy(adjective, weak, delicate, ill, sick) |
| flinching(verb, flinching) |
| floundering(verb, failing) |
| fluctuating(adjective, weak, uncertain, doubtful, hesitant) |
| frail(adjective, weak, delicate, ill, sick) |
| imperceptible(adjective, weak, pale, faded) |
| inconstant(unreliable, uneven, variable, erratic, random) |
| indisposition(noun, delay, weakness, doubt, uncertainty) |
| irregular(adjective, variable, erratic, random, haphazard) |
| lazy(adjective, uncertain, shy, doubtful, hesitant) |
| low(adjective, weak, pale, faded) |
| moderate(weak, pale, faded) |
| muffled(adjective, weak, pale, confused, rambling) |
| nervous(adjective, weak, awkward, unstable, shy) |
| pale(adjective, weak, faded) |