The Collaborative International Dictionary of English v.0.48:

Leger \Leg"er\, a. [F. l['e]ger, fr. LL. (assumed) leviarius,
   fr. L. levis light in weight. See Levity.]
   Light; slender; slim; trivial. [Obs. except in special
   phrases.] --Bacon.
   [1913 Webster]

   Leger line (Mus.), a line added above or below the staff to
      extend its compass; -- called also added line.
      [1913 Webster]

WordNet (r) 3.0 (2006):

leger line
    n 1: a short line; a notation for extending the range above or
         below the staff [syn: ledger line, leger line]