| introit | n. | psalm read or sung at beginning of the Mass (particularly as the celebrant approaches the Eucharist); introduction | ||
| intumescent | adj. | swollen | ||
| inure | v. | to habituate or to accustom (esp. to hardship, difficulty, pain, etc.) | ||
| invagination | n. | sheathing; intussusception, folding over onto itself | ||
| inveterate | adj. | firmly entrenched through habit or long practice | ||
| invidious | adj. | likely to incite ill will or odium; offensively prejudicial | ||
| invigilate | v. | to watch over students during an exam | ||
| inviolacy | n. | freedom from violation or desecration | ||
| invultuation | n. | creation of an image, esp. a waxen effigy for purposes of witchcraft | ||
| irenic | adj. | non-polemic, pacifying, tending to promote reconciliation | ||
| irid | n. | iris of the eye | ||
| Irish pennant | n. | untidy loose ends of rigging or lines | British | |
| iritis | n. | inflammation of the iris | ||
| ironicon | n. | backwards question mark, intended as a punctuation mark to denote irony; also called a percontation point | ||
| irredentist | adj. | of or related to policy of acquisition by a country of territory belonging to another because of historical or cultural ties; advocate of such policy | ||
| irrefragable | adj. | indisputable, undeniable | ||
| irremissibly | adv. | unforgivably, in a manner precluding all possibility of pardon | ||
| irreprehensible | adj. | blameless, innocent | ||
| irriguous | adj. | well-watered | archaic | |
| isarithm | n. | contour lines | ||
| isochrony | n. | state of occurring at same time or occupying same length of time; theory of linguistic division of time into equal parts | ||
| isogonic | adj. | having equal angles; esp., of lines demarcating points having equal magnetic declination | ||
| isonomy | n. | equality of persons before the law | ||
| ithyphallic | adj. | of the phallus carried in ancient Bacchus festivals; hence, of or pertaining to an erect penis | ||
| jabot | n. | decorative ruffle at neckline descending down the front of the blouse or shirt | ||
| jack-pudding | n. | buffoon, merry-andrew | ||
| Jackson ball | n. | hard penny candy, bull’s eye | obsolete | |
| jade | n. | vicious, worn-out, or worthless horse; disreputable woman | ||
| jagger | n. | pedlar; carrier | ||
| jake leg | n. | paralysis caused by drinking bootleg liquor made from denatured alcohol | ||
| jakes | n. | outhouse | idiom | |
| jamb | n. | either vertical element alongside a wall opening such as a door or window frame | ||
| jankers | n. | punishment detail with pointless tasks, inspections, and confinement to barracks | British | |
| jarvey | n. | hackney coachman | ||
| jauk | v. | to dawdle | Scots | |
| javelina | n. | collared peccary | ||
| jeepney | n. | two-bench jitney bus, usually with bright-colored and garish designs, commonly used throughout the Philippines | ||
| jehu | n. | fast driver, often furiously so; cabman | colloquial | |
| jejune | adj. | boring, uninteresting; lacking content or matter or nutritive substance; immature, juvenile | ||
| jeofail | n. | mistake in legal pleading; acknowledgement of such mistake | ||
| jess | n. | short leather strap tied around each leg of a hunting hawk, usu. with ring for attaching bird to its perch | ||
| jessie | n. | sissy, coward, effeminate boy or man | slang | |
| jetton | n. | token or counter of metal, etc. | ||
| jiggery-pokery | n. | trickery; manipulation | British | |
| jillflirt | n. | wanton, giddy young girl | archaic | |
| jingo | n. | bellicose patriot | ||
| jink | v. | to move jerkily; to elude | ||
| jipijapa | n. | Panama hat | ||
| jobsworth | n. | worker or official using their petty authority unhelpfully and refusing to make accommodations for particular cases | British | |
| jockey box | n. | insulated container using ice, water, and coils to provide cold beverages at at temporary location; container on conveyance for tools, etc. |
