The Collaborative International Dictionary of English v.0.48:

Extra- \Ex"tra-\ [L., fr. exter. See Exterior.]
   A Latin preposition, denoting beyond, outside of; -- often
   used in composition as a prefix signifying outside of,
   beyond, besides, or in addition to what is denoted by the
   word to which it is prefixed.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Extra \Ex"tra\, a.
   Beyond what is due, usual, expected, or necessary;
   additional; supernumerary; also, extraordinarily good;
   superior; as, extra work; extra pay. "By working extra
   hours." --H. Spencer.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Extra \Ex"tra\, n.; pl. Extras.
   1. Something in addition to what is due, expected, or
      customary; esp., an added charge or fee, or something for
      which an additional charge is made; as, at some hotels air
      conditioning is an extra.
      [Webster 1913 Suppl.]

   2. An edition of a newspaper issued at a time other than the
      regular one.
      [Webster 1913 Suppl.]

   3. (Cricket) A run, as from a bye, credited to the general
      score but not made from a hit.
      [Webster 1913 Suppl.]

   4. Something of an extra quality or grade.
      [Webster 1913 Suppl.]