1. [n]  the property possessed by a line or surface that departs from the vertical; "the tower had a pronounced tilt"; "the ship developed a list to starboard"; "he walked with a heavy inclination to the right"
2. [adj]  lacking excess flesh; "you can't be too rich or too thin"; "Yon Cassius has a lean and hungry look"-Shakespeare
3. [adj]  not profitable or prosperous; "a lean year"
4. [adj]  lacking in mineral content or combustible material; "lean ore"; "lean fuel"
5. [adj]  (metallurgy) low in mineral content; "a lean ore"
6. [adj]  containing little excess; "a lean budget"; "a skimpy allowance"
7. [v]  rely on for support; "We can lean on this man"
8. [v]  cause to lean or incline; "He leaned his rifle against the wall"
9. [v]  to incline or bend from a vertical position; "She leaned over the banister"
10. [v]  have a tendency or disposition to do or be something; be inclined; "She tends to be nervous before her lectures"; "These dresses run small"; "He inclined to corpulence"

1. \Lean\ (l[=e]n), v. t. [Icel. leyna; akin to G. l["a]ugnen
   to deny, AS. l[=y]gnian, also E. lie to speak falsely.]
   To conceal. [Obs.] --Ray.
   

2. \Lean\ (l[=e]n), v. i. [imp. & p. p. {Leaned} (l[=e]nd),
   sometimes {Leant} (l[e^]nt); p. pr. & vb. n. {Leaning}.] [OE.
   lenen, AS. hlinian, hleonian, v. i.; akin to OS. hlin[=o]n,
   D. leunen, OHG. hlin[=e]n, lin[=e]n, G. lehnen, L. inclinare,
   Gr. kli`nein, L. clivus hill, slope. [root]40. Cf.
   {Declivity}, {Climax}, {Incline}, {Ladder}.]
   1. To incline, deviate, or bend, from a vertical position; to
      be in a position thus inclining or deviating; as, she
      leaned out at the window; a leaning column. ``He leant
      forward.'' --Dickens.
   2. To incline in opinion or desire; to conform in conduct; --
      with to, toward, etc.
            They delight rather to lean to their old customs.
                                                  --Spenser.
   3. To rest or rely, for support, comfort, and the like; --
      with on, upon, or against.
            He leaned not on his fathers but himself.
                                                  --Tennyson.
   

3. \Lean\, v. t. [From {Lean}, v. i.; AS. hl[=ae]nan, v. t.,
   fr. hleonian, hlinian, v. i.]
   To cause to lean; to incline; to support or rest. --Mrs.
   Browning.
         His fainting limbs against an oak he leant. --Dryden.
   

4. \Lean\ (l[=e]n), a. [Compar. {Leaner} (l[=e]n"[~e]r);
   superl. {Leanest}.] [OE. lene, AS. hl[=ae]ne; prob. akin to
   E. lean to incline. See {Lean}, v. i. ]
   1. Wanting flesh; destitute of or deficient in fat; not
      plump; meager; thin; lank; as, a lean body; a lean cattle.
   2. Wanting fullness, richness, sufficiency, or
      productiveness; deficient in quality or contents; slender;
      scant; barren; bare; mean; -- used literally and
      figuratively; as, the lean harvest; a lean purse; a lean
      discourse; lean wages. ``No lean wardrobe.'' --Shak.
            Their lean and fiashy songs.          --Milton.
            What the land is, whether it be fat or lean. --Num.
                                                  xiii. 20.
            Out of my lean and low ability I'll lend you
            something.                            --Shak.
   3. (Typog.) Of a character which prevents the compositor from
      earning the usual wages; -- opposed to {fat}; as, lean
      copy, matter, or type.
   Syn: slender; spare; thin; meager; lank; skinny; gaunt.
   

5. \Lean\, n.
   1. That part of flesh which consist principally of muscle
      without the fat.
            The fat was so white and the lean was so ruddy.
                                                  --Goldsmith.
   2. (Typog.) Unremunerative copy or work.
   

An experimental language from the University of Nijmegen and University of East Anglia, based on graph rewriting and useful as an intermediate language. Lean is descended from Dactl0.

Clean is a subset of Lean.

["Towards an Intermediate Language Based on Graph Rewriting", H.P. Barendregt et al in PARLE: Parallel Architectures and Languages Europe, G. Goos ed, LNCS 259, Springer 1987, pp.159-175].