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.]

Moby Thesaurus II by Grady Ward, 1.0:

213 Moby Thesaurus words for "extra":
   above, accessory, accident, accidental, added, addendum, addition,
   additional, additionally, adjunct, adscititious, adventitious,
   again, all included, also, altogether, amazingly,
   among other things, ancillary, and all, and also, and so, another,
   appendage, appurtenance, appurtenant, as a bonus, as well,
   ascititious, au reste, auxiliary, balance, beside, besides, beyond,
   bit player, bonus, casual, circumstantial, collateral,
   considerably, contingency, contingent, contributory, daily,
   daily newspaper, de trop, decoration, dividend, else, en plus,
   especially, exceptionally, excess, extra added attraction,
   extra dash, extra edition, extraordinarily, extremely, farther,
   figurant, figurante, filigree, filling, fillip, flourish,
   for lagniappe, fortuitous, fresh, frill, further, furthermore,
   gazette, gratuity, happenstance, held back, held in reserve,
   held out, in abeyance, in addition, in hand, incidental,
   inessential, inter alia, into the bargain, item, kicker, lagniappe,
   leftover, likewise, margin, markedly, mere chance, mint, more,
   moreover, mute, national newspaper, neighborhood newspaper, new,
   news, newspaper, newspaper of record, nonessential, not-self,
   notably, noticeably, occasional, odd, off, on the side, on top of,
   original, ornament, other, out-of-the-way, over, over and above,
   overage, overmeasure, overplus, overrun, overset, overstock,
   oversupply, padding, paper, part-time, particularly, plus,
   pourboire, premium, pristine, put aside, put by, rag, rarely,
   remainder, remaining, remarkably, reserve, saved, secondary, sheet,
   side, similarly, something extra, spare, spear-carrier, special,
   special edition, stand-in, standby, stored, strikingly, stuffing,
   subsidiary, substitute, supe, super, superadded, superaddition,
   superfluous, supernumerary, supervenient, supplement, supplemental,
   supplementary, support, supporting actor, supporting cast,
   surcharge, surplus, surplusage, surprisingly, suspended, tabloid,
   then, therewith, tip, to boot, to spare, too, trimming, twist,
   ulterior, unapplied, unbeaten, uncommon, uncommonly, unconsumed,
   understudy, unemployed, unessential, unexercised, unexpectedly,
   unexpended, unhandled, unspent, untapped, untouched, untrodden,
   unused, unusually, unutilized, very, waived, walk-on,
   walking gentleman, weekly, weekly newspaper, wrinkle, yet



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

EXTRA
       EXecutionTRace Analyser (IBM, OS/2)