incorregible, incorrigible.
incredulidad, f., incredulity.
incrédulo, -a, incredulous.
increíble, incredible.
indecible, unspeakable, ineffable.
indeciso, -a, uncertain, indefinite.
indefinable, indefinable.
indescriptible, indescribable.
indicar, to indicate.
indiferente, indifferent.