ul ‧ te ‧ ri ‧ or /ʌlˈtɪ ə riə $ -ˈtɪriər/ BrE AmE adjective
[ Date: 1600-1700 ; Language: Latin ; Origin: 'farther' , from ulter 'in a position beyond' , from uls 'beyond' ]
ulterior motive/purpose etc a reason for doing something that you deliberately hide in order to get an advantage for yourself:
He’s just being nice. I don’t think he has any ulterior motives.