| Term | Definition |
| invective (n) | abuse |
| invert (v) | turn upside down or inside out |
| inveterate (adj) | deep-rooted; habitual |
| invidious (adj) | designed to create ill will or envy |
| inviolability (n) | security from being destroyed, corrupted, or profaned |
| invoke (v) | call upon; ask for |
| iota (n) | very small quantity |
| irascible (adj) | irritable; easily angered |
| irksome (adj) | annoying; tedious |
| irreconcilable (adj) | incompatible; not able to be resolved |
| irreparable (adj) | not able to be corrected or repaired |
| irrepressible (adj) | unable to be restrained or held back |
| irresolute (adj) | uncertain how to act; weak |
| irreverent (adj) | lacking proper respect |
| irrevocable (adj) | unalterable |
| itinerant (adj) | wandering; trableing |