Real Dictionary

lean
adjective: If meat is lean, it does not have very much fat.
adjective: If you describe someone as lean, you mean that they are thin but look strong and healthy.
verb: If you lean on or against someone or something, you rest against them so that they partly support your weight. If you lean an object on or against something, you place the object so that it is partly supported by that thing.
verb: When you lean in a particular direction, you bend your body in that direction.

lean in American English 1
to bend or deviate from an upright position; stand at a slant; incline
intransitive verb: to incline or bend from a vertical position
transitive verb: to incline or bend

lean in American English 2
with little flesh or fat; thin; spare
adjective: without much flesh or fat; not plump or fat; thin
noun: the part of flesh that consists of muscle rather than fat

Lean in British English
noun: Sir David. 1908–91, English film director. His films include In Which We Serve (1942), Blithe Spirit (1945), Brief Encounter (1946), Great Expectations (1946), Oliver Twist (1948), The Bridge on the River Kwai (1957), Lawrence of Arabia (1962), Dr Zhivago

lean in British English 1
verb: to rest or cause to rest against a support

lean in British English 2
adjective: (esp of a person or an animal) having no surplus flesh or bulk; not fat or plump
noun: the part of meat that contains little or no fat