The Collaborative International Dictionary of English v.0.48:

L \L\ ([e^]l), n.
   1. An extension at right angles to the length of a main
      building, giving to the ground plan a form resembling the
      letter L; sometimes less properly applied to a narrower,
      or lower, extension in the direction of the length of the
      main building; a wing. [Written also ell.]
      [1913 Webster]

   2. (Mech.) A short right-angled pipe fitting, used in
      connecting two pipes at right angles. [Written also
      ell.]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ell \Ell\, n. [AS. eln; akin to D. el, elle, G. elle, OHG.
   elina, Icel. alin, Dan. alen, Sw. aln, Goth. alenia, L. ulna
   elbow, ell, Gr. ? elbow. Cf. Elbow, Alnage.]
   A measure for cloth; -- now rarely used. It is of different
   lengths in different countries; the English ell being 45
   inches, the Dutch or Flemish ell 27, the Scotch about 37.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ell \Ell\, n. (Arch.)
   See L.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ell
    n 1: an extension at the end and at right angles to the main
         building

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "ell":
   L, addition, angle, annex, apex, arm, bend, bifurcation, bight,
   block, cant, chevron, coin, corner, crank, crook, crotchet,
   deflection, dogleg, elbow, extension, fork, furcation, hook,
   inflection, knee, nook, point, quoin, swerve, veer, vertex, wing,
   zag, zig, zigzag



Bouvier's Law Dictionary, Revised 6th Ed (1856):

ELL. A measure of length. In old English the word signifies arm, which sense
it still retains in the word elbow. Nature has no standard of measure. The
cubit, the ell, the span, palm, hand, finger, (being taken from the
individual who uses them) varies. So of the foot, pace, mile, or mille
passuum. See Report on Weights and Measures, by the Secretary of State of
the United. States, Feb. 22, 1821; Fathom.