Duty  n. (pl. -ies) 1 a moral or legal obligation; responsibility. B binding force of what is right. 2 tax on certain goods, imports, etc. 3 job or function arising from a business or office (playground duty). 4 deference; respect due to a superior.  do duty for serve as or pass for (something else). On (or off) duty working (or not working). [anglo-french: related to *due]