Adjective principal has 1 sense
  1. chief, main, primary, principal - 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"
    Antonym: unimportant (indirect, via important)
,Noun principal has 5 senses
  1. principal - the original amount of a debt on which interest is calculated
    --1 is a kind of
    --1 is a part of loan
  2. principal, school principal, head teacher, head - the educator who has executive authority for a school; "she sent unruly pupils to see the principal"
    --2 is a kind of educator, pedagogue
    --2 has particulars:
     chancellor; headmaster, schoolmaster, master; headmistress
  3. star, principal, lead - an actor who plays a principal role
    --3 is a kind of actor, histrion, player, thespian, role player
    --3 has particulars:
     co-star; film star, movie star; idol, matinee idol; television star, TV star
  4. principal, corpus, principal sum - capital as contrasted with the income derived from it
    --4 is a kind of capital
  5. principal, dealer - the major party to a financial transaction at a stock exchange; buys and sells for his own account
    --5 is a kind of financier, moneyman
    --5 has particulars: broker-dealer