Intellect, n.
Etymology: [L. intellectus, fr. intelligere, intellectum, to understand: cf. intellect. See Intelligent.]
(Metaph.)
The part or faculty of the human soul by which it knows, as distinguished from the power to feel and to will; sometimes, the capacity for higher forms of knowledge, as distinguished from the power to perceive objects in their relations; the power to judge and comprehend; the thinking faculty; the understanding.
Shades of meaning
Fernald has no entry of its own for intellect; he lists it under mind.
Where he writes about it:
Mind, in a general sense, includes all the powers of sentient being apart from the physical factors in bodily faculties and activities; in a limited sense, mind is nearly synonymous with intellect, but includes disposition, or the tendency toward action, as appears in the phrase "to have a mind to work." As the seat of mental activity, brain (colloquially brains) is often used as a synonym for mind, intellect, intelligence. — from mind
The instinct of animals is now held by many philosophers to be of the same nature as the intellect of man, but inferior and limited; yet the apparent difference is very great. — from mind
The soul includes the intellect, sensibilities, and will; beyond what is expressed by the word mind, the soul denotes especially the moral, the immortal nature; we say of a dead body, the soul (not the mind) has fled. — from mind
Sense may be an antonym of intellect, as when we speak of the sense of hearing; but sense is used also as denoting clear mental action, good judgment, acumen; as, he is a man of sense, or, he showed good sense; sense, even in its material signification, must be reckoned among the activities of mind, tho dependent on bodily functions; the mind, not the eye, really sees; the mind, not the ear, really hears. — from mind
The intellect is that assemblage of faculties which is concerned with knowledge, as distinguished from emotion and volition. — from mind