| Term | Definition |
| hackneyed | worn out by overuse |
| hapless | unfortunate, having bad luck |
| harbinger | precursor, sign of something to come |
| harrowing | extremely distressing, terrifying |
| hermetic | tightly sealed |
| hidebound | excessively rigid, dry and stiff |
| hinterland | wilderness |
| hoary | very old, whitish or gray from age |
| hyperbole | purposeful exaggeration for effect |
| iconoclast | one who attacks traditional beliefs |
| idiosyncracy | peculiarity of temperament, eccentricity |
| ignominious | disgraceful and dishonorable |
| ilk | type or kind |
| imbue | to infuse, to dye, wet, moisten |
| immutable | unchangeable, invariable |
| impecunious | poor, having no money |
| impervious | impossible to penetrate, incapable of being affected |
| impetuous | quick to act without thinking |
| importune | to ask repeatedly; beg |
| improvident | without planning or foresight; negligent |
| impugn | to call into question; to attack verbally |
| incendiary | combustible, flammable, burning easily |
| incipient | beginning to exist or appear; in an initial stage |
| inculcate | to teach, impress in the mind |
| inculpate | to blame, charge with a crime |
| incursion | sudden invasion |
| indefatigable | never tired |
| indigent | very poor |
| indignant | angry, incensed, offended |
| indolent | habitually lazy, idle |
| indubitable | unquestionable |
| inert | unable to move, tending to inactivity |
| inexorable | inflexible, unyielding |
| ingenious | original, clever, inventive |
| ingenuous | straightforward, open; naive and unsophisticated |
| ingress | entrance |
| inimical | hostile, unfriendly |
| iniquity | sin, evil act |
| insidious | sly, treacherous, devious |
| interdict | to forbid, prohibit |
| interloper | trespasser |
| interpolate | to insert; to change by adding new words or material |
| interpose | to insert; to intervene |
| intransigent | uncompromising, refusing to be reconciled |
| inure | to harden, to accustom; to become used to |
| invective | verbal abuse |
| invidious | envious, obnoxious |