leafleaf1 /lif/ ●●● noun (plural leaves /livz/ ) 1 [countable] science, biology one of the flat green parts of a plant that are joined to its stem or branches: There are still some leaves on the trees.2[countable] a part of the top of a table that can be added to make the table larger3[uncountable] gold or silver in a very thin sheet → turn over a new leaf at turn1