whereat Meaning, Definition & Usage
Where*at" adverb
Definitions
-  At which; upon which; whereupon; -- used relatively. They vote; whereat his speech he thus renews. Milton. Whereat he was no less angry and ashamed than desirous to obey Zelmane. Sir P. Sidney. 
-  At what; -- used interrogatively; as, whereat are you offended?