Conjunction
At which; upon which; whereupon; -- used relatively.
At what; -- used interrogatively; as, whereat are you offended?
Source: Webster's dictionaryWhereat some one of the loquacious Lot - I think a Sufi pipkin-waxing hot - "All this of Pot and Potter - Tell me then, Who is the Potter, pray, and who the Pot?" Omar Khayyám
Alas, when We came once again, We beheld you fleeing from Us, whereat the eye of My loving-kindness wept sore over My people." Source: Internet
His wife chides him: whereat he waxes wroth, beats her, and tells his comrades what they know better than he. Source: Internet