The Collaborative International Dictionary of English v.0.48:

lowercase \low"er*case`\, Lower-case \Low"er-case`\, a. (Print.)
   Pertaining to, or kept in, the lower case; -- used to denote
   the small letters, in distinction from capitals and small
   capitals; as, lowercase letters a and b and c etc..
   Contrasted with uppercase. See the Note under 1st Case,
   n., 3.
   [1913 Webster]