improvident adj. Lacking foresight or thrift.
improvise v. To do anything extemporaneously or offhand.
imprudent adj. Heedless.
impudence n. Insolent disrespect.
impugn v. To assail with arguments, insinuations, or accusations.
impulsion n. Impetus.
impulsive adj. Unpremeditated.
impunity n. Freedom from punishment.
impure adj. Tainted.
impute v. To attribute.
inaccessible adj. Difficult of approach.
inaccurate adj. Not exactly according to the facts.
inactive adj. Inert.
inadequate adj. Insufficient.
inadmissible adj. Not to be approved, considered, or allowed, as testimony.
inadvertent adj. Accidental.
inadvisable adj. Unadvisable.
inane adj. Silly.
inanimate adj. Destitute of animal life.
inapprehensible adj. Not to be understood.
inapt adj. Awkward or slow.
inarticulate adj. Speechless.
inaudible adj. That can not be heard.
inborn adj. Implanted by nature.
inbred adj. Innate.
incandescence n. The state of being white or glowing with heat.
incandescent adj. White or glowing with heat.
incapacitate v. To deprive of power, capacity, competency, or qualification.
incapacity n. Want of power to apprehend, understand, and manage.
incarcerate v. To imprison.
incendiary n. Chemical or person who starts a fire-literally or figuratively.
incentive n. That which moves the mind or inflames the passions.
inception n. The beginning.
inceptive adj. Beginning.
incessant adj. Unceasing.
inchmeal adv. Piecemeal.
inchoate adj. Incipient.
inchoative n. That which begins, or expresses beginning.
incidence n. Casual occurrence.
incident n. A happening in general, especially one of little importance.
incidentally adv. Without intention.
incinerate v. To reduce to ashes.
incipience n. Beginning.
incipient adj. Initial.
incisor n. A front or cutting tooth.
incite v. To rouse to a particular action.
incitement n. That which moves to action, or serves as an incentive or stimulus.
incoercible adj. Incapable of being forced, constrained, or compelled.
incoherence n. Want of connection, or agreement, as of parts or ideas in thought, speech, etc.
incoherent adj. Not logically coordinated, as to parts, elements, or details.
incombustible adj. That can not be burned.
incomparable adj. Matchless.
incompatible adj. Discordant.
incompetence n. General lack of capacity or fitness.
incompetent adj. Not having the abilities desired or necessary for any purpose.
incomplete adj. Lacking some element, part, or adjunct necessary or required.
incomprehensible adj. Not understandable.
incompressible adj. Resisting all attempts to reduce volume by pressure.
inconceivable adj. Incomprehensible.
incongruous adj. Unsuitable for the time, place, or occasion.
inconsequential adj. Valueless.
inconsiderable adj. Small in quantity or importance.
inconsistent adj. Contradictory.
inconstant adj. Changeable.
incontrovertible adj. Indisputable.
inconvenient adj. Interfering with comfort or progress.
indefensible adj. Untenable.
indefinitely adv. In a vague or uncertain way.
indelible adj. That can not be blotted out, effaced, destroyed, or removed.
indescribable adj. That can not be described.
indestructible adj. That can not be destroyed.
indicant adj. That which points out.
indicator n. One who or that which points out.
indict v. To find and declare chargeable with crime.
indigence n. Poverty.
indigenous adj. Native.
indigent adj. Poor.
indigestible adj. Not digestible, or difficult to digest.
indigestion n. Difficulty or failure in the alimentary canal in changing food into absorptive nutriment.
indignant adj. Having such anger and scorn as is aroused by meanness or wickedness.
indignity n. Unmerited contemptuous conduct or treatment.
indiscernible adj. Not perceptible.
indiscreet adj. Lacking wise judgment.
indiscriminate adj. Promiscuous.
indispensable adj. Necessary or requisite for the purpose.
indistinct adj. Vague.
indivertible adj. That can not be turned aside.
indivisible adj. Not separable into parts.
indolence n. Laziness.
indolent adj. Habitually inactive or idle.
indomitable adj. Unconquerable.
induct v. To bring in.
indulgence n. The yielding to inclination, passion, desire, or propensity in oneself or another.
indulgent adj. Yielding to the desires or humor of oneself or those under one's care.
inebriate v. To intoxicate.
inedible adj. Not good for food.
ineffable adj. Unutterable.
inefficient adj. Not accomplishing an intended purpose.
inefficiency n. That which does not accomplish an intended purpose.
ineligible adj. Not suitable to be selected or chosen.
inept adj. Not fit or suitable.
inert adj. Inanimate.
inestimable adj. Above price.
inevitable adj. Unavoidable.
inexcusable adj. Not to be justified.
inexhaustible adj. So large or furnishing so great a supply as not to be emptied, wasted, or spent.
inexorable adj. Unrelenting.
inexpedient adj. Unadvisable.
inexpensive adj. Low-priced.
inexperience n. Lack of or deficiency in experience.
inexplicable adj. Such as can not be made plain.
inexpressible adj. Unutterable.
inextensible adj. Of unchangeable length or area.
infallible adj. Exempt from error of judgment, as in opinion or statement.
infamous adj. Publicly branded or notorious, as for vice, or crime.
infamy n. Total loss or destitution of honor or reputation.
inference n. The derivation of a judgment from any given material of knowledge on the ground of law.
infernal adj. Akin to or befitting hell or its occupants.
infest v. To be present in such numbers as to be a source of annoyance, trouble, or danger.
infidel n. One who denies the existence of God.
infidelity n. Disloyalty.
infinite adj. Measureless.
infinity n. Boundless or immeasurable extension or duration.
infirm adj. Lacking in bodily or mental strength.
infirmary n. A place for the reception or treatment of the sick.
infirmity n. A physical, mental, or moral weakness or flaw.
inflammable adj. Easily set on fire or excited.
inflammation n. A morbid process in some part of the body characterized by heat, swelling, and pain.