n., adj., & v.
--n.
1. Psychol. a person predominantly concerned with his or her own thoughts and feelings rather than with external things.
2 a shy inwardly thoughtful person.
--adj. (also introverted) typical or characteristic of an introvert.
--v.tr.
1. Psychol. direct (one's thoughts or mind) inwards.
2 Zool. withdraw (an organ etc.) within its own tube or base, like the finger of a glove.
Derivatives:
introversion n. introversive adj. introverted adj. introvertive adj.
Etymology: INTRO- + vert as in INVERT