definition of
main

[1] #1 main s. [chief, primary, principal, master] 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". wn

[2] #2 main n. [briny] any very large body of (salt) water. wn

[3] #3 main n. a principal pipe in a system that distributes water or gas or electricity or that collects sewage. wn

[4] #4 main a. [independent] (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". wn