imperfection, n. [defect], [blemish], [shortcoming], [infirmity], foible, [deformity], [disfigurement], [vice], [frailty], [fallibility].
imperious, a. [despotic], magisterial, [domineering], [dictatorial], [tyrannical], [imperative].
imperishable, a. [permanent], indestructible, [enduring].
impersonate, v. [personate]; personify.
impersonation, n. [personation], impersonating; impersonification.
impersonator, n. [mimic], personator, mime, [actor].
impertinent, a. irrelevant, inapplicable, [impudent], [saucy], [rude], [insolent], malapert, [flippant].
impervious, a. impermeable, [impenetrable], imperviable.
impetus, n. [momentum], [force], [impulse], [incentive].
impish, a. malignant.