subterranean, subterraneous, ulterior -- (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)
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)
later, ulterior, posterior -- (coming at a subsequent time or stage; "without ulterior argument"; "the mood posterior to")
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