Source: https://www.ielts-mentor.com/46-ielts-vocabulary/561-ielts-vocabulary-i-part-1
Timestamp: 2019-04-22 03:24:15+00:00

Document:
ichthyology n. The branch of zoology that treats of fishes.
ichthyosaurs n. A fossil reptile.
iciness n. The state of being icy.
icon n. An image or likeness.
idealize v. To make to conform to some mental or imaginary standard.
idiom n. A use of words peculiar to a particular language.
idiosyncrasy n. A mental quality or habit peculiar to an individual.
idolize v. To regard with inordinate love or admiration.
ignoble adj. Low in character or purpose.
Iliad n. A Greek epic poem describing scenes from the siege of Troy.
illegal adj. Not according to law.
illiterate adj. Having little or no book-learning.
illogical adj. Contrary to the rules of sound thought.
illuminant n. That which may be used to produce light.
illuminate v. To supply with light.
illumine v. To make bright or clear.
illusion n. An unreal image presented to the senses.
illusory adj. Deceiving or tending to deceive, as by false appearance.
imaginable adj. That can be imagined or conceived in the mind.
imbibe v. To drink or take in.
imbroglio n. A misunderstanding attended by ill feeling, perplexity, or strife.
imbrue v. To wet or moisten.
imitation n. That which is made as a likeness or copy.
imitator n. One who makes in imitation.
immaculate adj. Without spot or blemish.
immaterial adj. Of no essential consequence.
immense adj. Very great in degree, extent, size, or quantity.
immerse v. To plunge or dip entirely under water or other fluid.
immersion n. The act of plunging or dipping entirely under water or another fluid.
immigrant n. A foreigner who enters a country to settle there.
immigrate v. To come into a country or region from a former habitat.
imminence n. Impending evil or danger.
imminent adj. Dangerous and close at hand.
immiscible adj. Separating, as oil and water.
immoral adj. Habitually engaged in licentious or lewd practices.
immortalize v. To cause to last or to be known or remembered throughout a great or indefinite length of time.
immune adj. Exempt, as from disease.
impair v. To cause to become less or worse.
impalpable adj. Imperceptible to the touch.
impassable adj. That can not be passed through or over.
impassible adj. Not moved or affected by feeling.
impassive adj. Unmoved by or not exhibiting feeling.
impatience n. Unwillingness to brook delays or wait the natural course of things.
impecunious adj. Having no money.
impede v. To be an obstacle or to place obstacles in the way of.
impel v. To drive or urge forward.
impend v. To be imminent.
imperfectible adj. That can not be perfected.
imperious adj. Insisting on obedience.
impersonal adj. Not relating to a particular person or thing.
impersonate v. To appear or act in the character of.
impious adj. Characterised by irreverence or irreligion.
impliable adj. Capable of being inferred.
importation n. The act or practice of bringing from one country into another.
importunate adj. Urgent in character, request, or demand.
importune v. To harass with persistent demands or entreaties.
impotent adj. Destitute of or lacking in power, physical, moral, or intellectual.
impoverish v. To make indigent or poor.
impregnable adj. That can not be taken by assault.
impregnate v. To make pregnant.
impromptu n. Anything done or said on the impulse of the moment.
improper adj. Not appropriate, suitable, or becoming.
impropriety n. The state or quality of being unfit, unseemly, or inappropriate.
improvident adj. Lacking foresight or thrift.
improvise v. To do anything extemporaneously or offhand.
impugn v. To assail with arguments, insinuations, or accusations.
impunity n. Freedom from punishment.

References: v. 
 v. 
 v. 
 v. 
 v. 
 v. 
 v. 
 v. 
 v. 
 v. 
 v. 
 v. 
 v. 
 v. 
 v. 
 v. 
 v. 
 v. 
 v.