146 VOCABULARY FOR TOEFL iBT
indefatigable (in·di·'fat· ̆·a ̆·be ̆l) adj. not easily exhausted or fatigued; tireless.
The volunteers were indefatigable; they worked until every piece of trash was removed
from the beach.
indolent ('in·do ̆·le ̆nt) adj. 1. lazy, lethargic, inclined to avoid labor. 2. causing lit-
tle or no pain; slow to grow or heal. The construction foreman was hesitant to hire
Earl because of his reputation of being indolent.
indomitable (in·'dom·i·ta ̆·be ̆l) adj. not able to be vanquished or overcome,
unconquerable; not easily discouraged or subdued. The indomitable spirit of the
Olympic athletes was inspirational.
ineluctable (in·i·'luk·ta ̆·be ̆l) adj. certain, inevitable; not to be avoided or over-
come. The ineluctable outcome of the two-person race was that there would be one
winner and one loser.
inept (in·'ept) adj. 1. not suitable, inappropriate. 2. absurd, foolish. 3. incompe-
tent, bungling and clumsy. Trying to carry all her suitcases at once was an inept way
for Amanda to save time.
infidel ('in·fi·de ̆l) n. 1. a person with no religious beliefs. 2. a nonbeliever, one
who does not accept a particular religion, doctrine, or system of beliefs. Because
he did not subscribe to the beliefs of the party, the members considered him an infidel.
ingenuous (in·'jen·yoo·u ̆s) adj. 1. not cunning or deceitful, unable to mask feel-
ings; artless, frank, sincere. 2. lacking sophistication or worldliness. Don’s
expression of regret was ingenuous, for even though he didn’t know her well, he felt a
deep sadness when Mary died.
inimitable (i·'nim·i·ta ̆·be ̆l) adj. defying imitation, unmatchable. His performance
on the tennis court was inimitable, and he won three championships.
inscrutable (in·'scroo·ta ̆·be ̆l) adj. baffling, unfathomable, incapable of being
understood. It was completely inscrutable how the escape artist got out of the trunk.
insolent ('in·so ̆·le ̆nt) adj. haughty and contemptuous; brazen, disrespectful,
impertinent. Parents of teenagers often observe the insolent behavior that typically
accompanies adolescence.
insouciant (in·'soo·see·a ̆nt) adj. blithely unconcerned or carefree; nonchalant,
indifferent. Julian’s insouciant attitude about his finances will get him in trouble
someday.
interdict (in·te ̆r·'dikt) v. to prohibit, forbid. Carlos argued that the agriculture
department should interdict plans to produce genetically modified foods.