Pronunciation: (&thslash;ā),[key] —pron.pl.,poss.their or theirs,obj.them. 1. nominative plural of he, she, and it. 2. people in general: They say he's rich. 3. (used with an indefinite singular antecedent in place of the definite masculine he or the definite feminine she): Whoever is of voting age, whether they are interested in politics or not, should vote.