DAILY VOCABULARY WITH PICTURES. Loaf.

• loaf plural loaves
• 1 [countable] bread that is shaped and baked in one piece and can be cut into slices:
• a loaf of bread
• white/wholemeal/granary etc loaf British English
• a sliced loaf British English
• 2 [uncountable and countable] food that has been cut into very small pieces, pressed together, and baked:
• a meat loaf
• 3

   use your loaf

  British English old-fashioned used to tell someone to think more carefully about what they are doing

Definition from the Longman Dictionary of Contemporary English
Advanced Learner's Dictionary.