Great Cleave has a greater chance to hit more enemies than Cleave. This feat has a cooldown of 5 seconds. Like Cleave, Great Cleave also counts a full attack, dealing full special effect damage to all targets hit. This attack can doublestrike and is affected by your Attack Speed.
Prior to Update 45, it would also produce a glancing blow to each target (if using an appropriate weapon that allows them). Glancing blows have now been replaced by Strikethrough, which does not benefit Cleave or Great Cleave.