pronoun, nom. it, poss. its or ( Obs. or Dial. ) it, obj. it; pl. nom. they, poss. their or theirs, obj. them; noun
1. (used to represent an inanimate thing understood, previously mentioned, about to be mentioned, or present in the immediate context): It has whitewall tires and red upholstery. You can't tell a book by its cover.