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

• sunrise
• sunrise industry
• sunroof
• sunroom
• sunrose
• sunscreen
• sunset
• sunshade
• sunshine
• Sunshine State
• sunshine-roof
• sunshiny
• sunspot
• sunstone
• sunstroke
• sunstruck
• sunsuit
• suntan
• suntanned
• suntrap
• sunup
• sunward
• suo moto
• Suomi
• sup