| featureless |
| feckless(inferior, inadequate, limited, feeble, useless) |
| feeble(inadequate, limited, useless, vain, unsuccessful) |
| forceless(adjective, inferior, inadequate, limited, feeble) |
| frivolous(adjective, slight, lower, value, inferior) |
| frothy(adjective, slight, lower, value, inferior) |
| garbled |
| idle(inferior, inadequate, limited, feeble, useless) |
| illusory(adjective, unsubstantial) |
| impalpable(adjective, unsubstantial) |
| importless |
| impotent(inferior, inadequate, limited, feeble, useless) |
| inadequate(limited, feeble, useless, vain, unsuccessful) |
| incompetent(inadequate, limited, feeble, useless, vain) |
| inconsequential(adjective, slight, lower, value, inferior) |
| inconsiderable(adjective, slight, lower, value, inferior) |
| indecisive(inferior, inadequate, limited, feeble, useless) |
| indifferent(adjective, slight, lower, value, inferior) |
| inefficient(inferior, inadequate, limited, feeble, useless) |
| inept(inadequate, limited, feeble, useless, vain) |