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

• Ardea occidentalis
• ardeb
• Ardeidae
• ardency
• Ardennes
• Ardennes counteroffensive
• ardent
• ardent spirits
• ardently
• Ardisia
• Ardisia crenata
• Ardisia escallonoides
• Ardisia paniculata
• ardor
• ardour
• ARDS
• arduous
• arduously
• arduousness
• are
• area
• area 17 of Brodmann
• area bombing
• area code
• area of cardiac dullness