main in WordNet English dictionary

1. any very large body of (salt) water
   main  briny 
   
2. a principal pipe in a system that distributes water or gas or electricity or that collects sewage
   main 
   

1. most important element
   "the chief aim of living"; "the main doors were of solid glass"; "the principal rivers of America"; "the principal example"; "policemen were primary targets"; "the master bedroom"; "a master switch"
   chief  main  primary  principal  master 
   
2. (of a clause) capable of standing syntactically alone as a complete sentence
   "the main (or independent) clause in a complex sentence has at least a subject and a verb"
   independent  main 
   
3. of force; of the greatest possible intensity
   "by main strength"
   main