Webster's Revised Unabridged Dictionary · 1913

Introvert

Introvert , transitive verb

[Prefix intro- + Latin vertere, versum, to turn.]

1.
To turn or bend inward.
Introverted toes. — Cowper
2.
To look within; to introspect. — Lew Wallace

Introvert , noun

1.
A person who is introverted; one concerned predominantly with himself or his own feelings. Contrasted with extrovert.
2.
A person who is shy.
3.
(Zoology) A part that can be introverted{1}.