1. Being or operating under the surface of the earth
   - subterranean 
2. Lying beyond what is openly revealed or avowed (especially being kept in the background or deliberately concealed)
   - subterranean, ulterior

See also: covert, subsurface

• Balaton
• balboa
• balbriggan
• balconied
• balcony
• bald
• bald cypress
• bald eagle
• bald-faced
• bald-faced hornet
• bald-headed
• bald-pated
• baldachin
• Balder
• balderdash
• baldhead
• baldie
• balding
• baldly
• baldness
• baldpate
• Baldr
• baldric
• baldrick
• Baldwin