| Term | Definition |
| hypocrite | an insincere person; one who pretends to have feelings he doesn't really possess |
| idolatry | the worship of objects or people as gods |
| imbue | to fill, as with a strong dye or a strong feeling |
| imminent | about to take place; happening soon |
| immutable | unable to change |
| impair | weaken in strength or value |
| impasse | a situation from which you cannot escape; stalemate |
| impassive | without feeling; expressionless |
| impede | get in the way; hinder |
| impetuous | making quick decisions and taking sudden action; hasty; impulsive |
| impostor | pretender |
| impudence | rudeness; insolence |
| inadvertent | unintentional |
| inane | silly; insignificant |
| inaugurate | begin; induct into |
| incessant | continuous; endless |
| inchoate | not yet fully developed |
| incite | arouse to action; stir up; foment |
| incompatible | incapable of existing together in peace |
| incongruous | out of place |
| incorrigible | impossible to correct, control, or discipline |
| incredulous | unwilling or unable to believe |
| indict | charge with a crime; accuse |
| indigent | very poor |
| indolent | lazy |
| induce | cause to happen; bring about |
| inert | lacking movement; inactive; sluggish |
| infallible | incapable of making a mistake |
| infamy | a bad reputation; notoriety |
| infer | to figure out, based on given information; conclude; deduce |
| infiltrate | penetrate by passing through gaps; enter secretly and become established, such as a spy might do in an enemy organization |
| ingenuous | naive; unsophisticated; inexperienced |
| innate | having a quality that arises from within, rather than learned or acquired from the outside; native; inborn |
| innocuous | harmless; inoffensive |
| innovation | a new idea or product; a new way of doing something that is so much better, it causes others to copy it |
| inscrutable | mysterious |
| insipid | dull; flat; without sparkle or flavor |
| insolent | rude; haughty |
| insolvent | unable to pay bills; bankrupt |
| intermittent | occurring at intervals; periodic; not constant or continual |
| intractable | stubborn; immovable |
| intrinsic | located within the very nature of an object or person; inherent |
| invert | turn upside down or inside out; reverse position |
| irascible | easily angered |
| irony | an unexpected outcome, or the use of a word that is the opposite of its literal meaning |
| irresolute | indecisive; unsure |
| irreverent | disrespectful |
| jargon | specialized language used by a particular group |
| jaundice | yellow; or, envy or resentment |
| jaunty | lively; perky; sprightly |
| jeopardy | the threat or possibility of danger |
| jettison | to throw overboard; to discard |
| jocular | joking; playful; jesting; witty |
| jubilant | filled with joy |
| judicious | wise; making good decisions |
| juncture | point in time, especially a crucial one; joint or connection |
| juxtapose | to place side-by-side |
| kindle | to start a fire; ignite; arouse |
| kinetic | in motion; active |
| laconic | quiet; of few words; terse |
| lament | express sorrow; complain |
| languish | lose energy or motivation; become weak or depressed |
| latent | existing but inactive, such as a certain quality; dormant or still; invisible |
| laud | praise; worship; extol |
| legacy | something inherited, either from an ancestor or from the past itself |
| lethargic | tired; sluggish; drowsy |
| levity | lightness; playfulness; jocularity |
| lionize | to put someone onto a pedestal; to treat with great respect |
| listless | tired; sluggish; lacking drive |
| loath | reluctant; unwilling |
| loathe | to hate |