pronoun

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The part of speech that substitutes for nouns or noun phrases and designates persons or things asked for, previously specified, or understood from the context.
2. n. Any of the words within this part of speech, such as he or whom.

Century Dictionary and Cyclopedia

1. n. In grammar, a word used instead of a noun to avoid the repetition of it; a demonstrative word, pointing to a person or thing, but not describing it otherwise than by designating position, direction, relation to the speaker, or the like; one of a small body of words, in Indo-European and other families of language, coming from a few roots, different from those from which come in general verbs and nouns, and having the office of designating rather than describing: they are believed to have borne an important part in the development of inflective structure in language. They are divided into various classes: personal (doubtless originally demonstrative), as I, thou, he, etc.; possessive, which are the adjective forms of the personal, as my, thy, his, etc.; demonstrative, as this, that, etc.; interrogative, as who, what, etc.; relative (which are always either demonstratives or interrogatives with changed office, implying an antecedent to which they refer or relate), as that, which, who, etc.; and indefinite, which are of various meaning, and shade off into ordinary nouns, as each, either, some, any, such, etc. Abbreviated pr., pron.

Wiktionary

1. n. grammar A type of noun that refers anaphorically to another noun or noun phrase, but which cannot ordinarily be preceded by a determiner and rarely takes an attributive adjective. English examples include I, you, him, who, me, my, each other.

GNU Webster's 1913

1. n. (Gram.) A word used instead of a noun or name, to avoid the repetition of it. The personal pronouns in English are I, thou or you, he, she, it, we, ye, and they.

WordNet 3.0

1. n. a function word that is used in place of a noun or noun phrase