- impend: To be imminent.
- imperative: Obligatory.
- imperceptible: Indiscernible.
- imperfectible: That can not be perfected.
- imperil: To endanger.
- imperious: Insisting on obedience.
- impermissible: Not permissible.
- impersonal: Not relating to a particular person or thing.
- impersonate: To appear or act in the character of.
- impersuadable: Unyielding.
- impertinence: Rudeness.
- imperturbable: Calm.
- impervious: Impenetrable.
- impetuosity: Rashness.
- impetuous: Impulsive.
- impetus: Any impulse or incentive.
- impiety: Irreverence toward God.
- impious: Characterized by irreverence or irreligion.
- implausible: Not plausible.
- impliable: Capable of being inferred.
- implicate: To show or prove to be involved in or concerned
- implicit: Implied.
- imply: To signify.
- impolitic: Inexpedient.
- importation: The act or practice of bringing from one country into another.
- importunate: Urgent in character, request, or demand.
- importune: To harass with persistent demands or entreaties.
- impotent: Destitute of or lacking in power, physical, moral, or intellectual.
- impoverish: To make indigent or poor.
- impracticable: Not feasible.
- impregnable: That can not be taken by assault.
- impregnate: To make pregnant.
- impromptu: Anything done or said on the impulse of the moment.
- improper: Not appropriate, suitable, or becoming.
- impropriety: The state or quality of being unfit, unseemly, or inappropriate.
- improvident: Lacking foresight or thrift.
- improvise: To do anything extemporaneously or offhand.
- imprudent: Heedless.
- impudence: Insolent disrespect.
- impugn: To assail with arguments, insinuations, or accusations.
- impulsion: Impetus.
- impulsive: Unpremeditated.
- impunity: Freedom from punishment.
- impure: Tainted.
- impute: To attribute.
- inaccessible: Difficult of approach.
- inaccurate: Not exactly according to the facts.
- inactive: Inert.
- inadequate: Insufficient.
- inadmissible: Not to be approved, considered, or allowed, as testimony.