lean

Etymology 1

From Middle English lenen (“to lean”), from Old English hleonian, hlinian (“to lean, recline, lie down, rest”), from Proto-West Germanic *hlinēn, from Proto-Germanic *hlināną (“to lean, incline”), from Proto-Indo-European *ḱley-. Cognate via Proto-Germanic with Middle Dutch leunen (“to lean”), German lehnen (“to lean”); via Proto-Indo-European with climate, cline.

verb

1. To incline, deviate, or bend, from a vertical position; to be in a position thus inclining or deviating.
   a leaning column
   She leaned out of the window.
2. (copulative) To incline in opinion or desire; to conform in conduct; often with to, toward, etc.
   I’m leaning towards voting Conservative in the next election.
   The Hispanic vote leans Democratic.
   But you ſay they do not accept of them, but delight rather to lean to their old Cuſtoms and Brehon Laws, though they be more unjuſt and alſo more inconvenient for the common People, as by your late Relation of them I have gathered. a. 1600, Edmund Spenser, “A View of the State of Ireland.[…]”, in The Works of Mr. Edmund Spenser, volume VI, London: Jacob Tonson[…], published 1715, →OCLC, page 1518
3. Followed by against, on, or upon: to rest or rely, for support, comfort, etc.
4. To hang outwards.
5. To press against.

noun

1. (of an object taller than its width and depth) An inclination away from the vertical.
   The trees had various leans toward gaps in the canopy.

Etymology 2

From Middle English lene (“lean”), from Old English hlǣne (“lean”), (cognate with Low German leen), perhaps from hlǣnan (“to cause to lean (due to hunger or lack of food)”), from Proto-Germanic *hlainijaną (“to cause to lean”). If so, then related to Old English hlinian, hleonian (“to lean”).

adj

1. (of a person or animal) Slim; not fleshy.
2. (of meat) Having little fat.
   lean steak cuts
3. Having little extra or little to spare; scanty; meagre.
   a lean budget
   a lean harvest
4. Having a low proportion or concentration of a desired substance or ingredient.
   A lean ore hardly worth mining.
   Running on too lean a fuel-air mixture will cause, among other problems, your internal combustion engine to heat up too much.
5. (printing, archaic) Of a character which prevents the compositor from earning the usual wages; opposed to fat.
   lean copy, matter, or type
6. (business) Efficient, economic, frugal, agile, slimmed-down; pertaining to the modern industrial principles of "lean manufacturing".
   lean management
   lean manufacturing
   Alcoa is now a lean and agile enterprise, after having split last year into two entities.

noun

1. (uncountable) Meat with no fat on it.
   Jack Sprat would eat no fat, / His wife would eat no lean. 1639, or earlier, Anon: Jack Sprat
2. (countable, biology) An organism that is lean in stature.
   The intermediates and leans are the predominant morphotypes found at the SE-NHR seamounts […] 1986, Southwest Fisheries Center (U.S.), Collected Reprints (issue 1)
   Obese Zuckers, compared to leans, consumed more food under free-feeding conditions. 2012, Obesity: New Insights for the Healthcare Professional, page 56

verb

1. To thin out (a fuel-air mixture): to reduce the fuel flow into the mixture so that there is more air or oxygen.
   He leaned the mixture in an effort to cause a backfire through the carburetor, the generally accepted method of breaking the ice loose. 1938 July, Harold Blaine Miller, Dupont Miller, “Weather Hop”, in Boys' Life, Boy Scouts of America, →ISSN, page 25
   Even the Pilot's Operating Handbooks (POH) for our training airplanes add to our paranoia with their insistence that we not lean the mixture until we're above 5000 feet density altitude. 2002 July, Tom Benenson, “Can Your Engine Run Too Lean?”, in Flying, volume 129, number 7, →ISSN, page 73

Etymology 3

From Icelandic leyna? Akin to German leugnen (“deny”). Compare lie (“speak falsely”).

verb

1. To conceal.

Etymology 4

Probably from the verb to lean (see etymology 1 above), supposedly because consumption of the intoxicating beverage causes one to "lean". Alternatively, possibly short for gasoline (“an alcoholic beverage made of vodka and energy drink”).

noun

1. (slang, US) A recreational drug based on codeine-laced promethazine cough syrup, especially popular in the hip hop community in the southeastern United States.
   Eyes real tight 'cause I'm chokin' the creep; vision messed up 'cause I'm drinkin' the lean. 2005, “Stay Fly”, in Jordan Houston, Darnell Carlton, Paul Beauregard, Premro Smith, Marlon Goodwin, David Brown, Willie Hutchinson (lyrics), Most Known Unknown, performed by Three 6 Mafia (featuring Young Buck, 8 Ball, and MJG), Sony BMG
   "What's in the cup, let me see that / Girl, where the rest of that promethazine at?" / She said, "Cool, gotta run out to my Cadillac though / And I'll be like Fat Joe, and bring the lean back" 2020, “Those Kinda Nights”, in Music to Be Murdered By, performed by Eminem ft. Ed Sheeran