Spare time which one must somehow occupy. The word kill here implies wasting or using time frivolously, and indeed this is the implication in Vanbrugh and Cibber’s play The Provok’d Husband (1728): “What think you, if we three sat soberly down to kill an hour at ombre [a card game]?” Ugo Betti (The Fugitive, 1953) took a more sober and critical view: “Killing time is the chief end of our society.”