subconscious= not fully aware; occurring below your level of thinking and awareness

 

subcutaneous= under the skin

 

subdue= to bring under control

 

subfreezing= below the freezing point

 

subirrigate= to water something from under the ground

 

subject= to put under someone else's control

 

submarine= a watercraft that stays under water

 

submerge= to put under water

 

subordinate= a person who is under someone else in rank or importance

 

subway= a passageway under the ground; an electric underground railway