er ‧ rat ‧ ic /ɪˈrætɪk/ BrE AmE adjective
[ Date: 1300-1400 ; Language: Old French ; Origin: erratique , from Latin errare ; ⇨ ↑ err ]
something that is erratic does not follow any pattern or plan but happens in a way that is not regular:
His breathing was becoming erratic.
his erratic behaviour
—erratically /-kli/ adverb :
He always drives erratically.