Definition of "luff"

noun:
- The vertical edge of a sail that is closest to the direction of the wind.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
verb:
- To shake due to being trimmed improperly.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
- To alter course to windward so that the sails luff. (Alternatively luff up).
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
- To alter the vertical angle of the jib of a crane so as to bring it level with the load.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License