Whereat \Where*at"\, adv. [1913 Webster] 1. At which; upon which; whereupon; -- used relatively. [1913 Webster] They vote; whereat his speech he thus renews. --Milton. [1913 Webster] Whereat he was no less angry and ashamed than desirous to obey Zelmane. --Sir P. Sidney. [1913 Webster] 2. At what; -- used interrogatively; as, whereat are you offended? [1913 Webster]