2DFlean meat does not have much fat on it [≠ fatty]
3a lean organization, company etc uses only as much money and as many people as it needs, so that nothing is wasted
4a lean period is a very difficult time because there is not enough money, business etc:
His wife was a source of constant support during thelean years.
WORD CHOICE: WORD CHOICE: thin, slim, skinny, slender, lean, slightThinis a general word meaning that someone has little fat on their body. It is usually, but not always, disapproving• He's much too thin. • Teenage girls all seem to want to be thin.Slimmeans thin in an attractive way• her lovely slim figureSkinnyis a fairly informal word meaning very thin, which is usually disapproving• ridiculously skinny modelsSlender, lean, and slight are used mostly in written English.Slendermeans thin in an attractive and graceful way• long slender legsLeanmeans thin and looking strong and fit• a tall, lean athleteSlightmeans thin and delicate-looking• Her brother was very slight and looked younger than he was. ➔ See alsothin
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.