lying beyond what is openly revealed or avowed (especially being kept in the background or deliberately concealed); "subterranean motives for murder"; "looked too closely for an ulterior purpose in all knowledge"- Bertrand Russell
明らかに見えるものや、公言のの裏にあること(特に背景に隠れているあるいは、故意に隠された)
ulterior
beyond or outside an area of immediate interest; remote; "a suggestion ulterior to the present discussion"; "without...any purpose, immediate or ulterior"- G.B.Shaw