1. the person that is used by the speaker of an utterance in referring to anything or to anyone other than the speaker or the one or ones being addressed.
2. a linguistic form or the group of linguistic forms referring to this grammatical person, as certain verb forms, pronouns, etc.: “He goes” contains a pronoun and a verb form in the third person.
3. in or referring to such a grammatical person or linguistic form: “He,” “she,” “it,” and “they” are third person pronouns, singular and plural, nominative case.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.