'Third person' definitions:

Definition of 'third person'

noun

Pronouns and verbs that are used to refer to something other than the speaker or addressee of the language in which they occur

From: GCIDE

Third \Third\ (th[~e]rd), a. [OE. thirde, AS. [thorn]ridda, fr. [thorn]r[imac], [thorn]re['o], three; akin to D. derde third, G. dritte, Icel. [thorn]ri[eth]i, Goth. [thorn]ridja, L. tertius, Gr. tri`tos, Skr. t[.r]t[imac]ya. See Three, and cf. Riding a jurisdiction, Tierce.]
1. Next after the second; coming after two others; -- the ordinal of three; as, the third hour in the day. "The third night." --Chaucer. [1913 Webster]
2. Constituting or being one of three equal parts into which anything is divided; as, the third part of a day. [1913 Webster]
Third estate. (a) In England, the commons, or the commonalty, who are represented in Parliament by the House of Commons. (b) In France, the tiers ['e]tat. See Tiers ['e]tat.
Third order (R. C. Ch.), an order attached to a monastic order, and comprising men and women devoted to a rule of pious living, called the third rule, by a simple vow if they remain seculars, and by more solemn vows if they become regulars. See Tertiary, n., 1.
Third person (Gram.), the person spoken of. See Person, n., 7.
Third sound. (Mus.) See Third, n., 3. [1913 Webster]