› open or available all day and all night without closing or stopping: Share trading is now a 24-hour industry. a 24-hour emergency line/helpline/hotline Responding to market pressure, they are offering 24-hour free telephone access. He recalls the scepticism that greeted the notion of 24-hour opening for US supermarkets.
› relating to one day, or happening only on one day: The service can only be used once in a 24-hour period.a 24-hour stoppage/strike Unified strike action spread over three twenty-four hour stoppages. → See also 24-hour clock, 24-hour society