[their] adj [ME, fr. their, pron., fr. ON theirra, gen. pl. demonstrative & personal pron.; akin to OE thaet that] (13c) 1: of or relating to them or themselves esp. as possessors, agents, or objects of an action "~ furniture" "~ verses" "~ being seen"
2: his or her: his, her, its--used with an indefinite third person singular antecedent "anyone in ~ senses --W. H. Auden" usage see they