The Collaborative International Dictionary of English v.0.48:

Pro \Pro\, prep. [L.; akin to prae before, Gr. ?, and E. for.
   See For, prep., and cf. Prior, a.]
   A Latin preposition signifying for, before, forth.
   [1913 Webster]

   Pro confesso [L.] (Law), taken as confessed. The action of
      a court of equity on that portion of the pleading in a
      particular case which the pleading on the other side does
      not deny.

   Pro rata. [L. See Prorate.] In proportion; proportion.

   Pro re nata [L.] (Law), for the existing occasion; as
      matters are.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pro \Pro\, adv.
   For, on, or in behalf of, the affirmative side; -- in
   contrast with con.
   [1913 Webster]

   Pro and con, for and against, on the affirmative and on the
      negative side; as, they debated the question pro and con;
      -- formerly used also as a verb.

   Pros and cons, the arguments or reasons on either side.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pro- \Pro-\ [L. pro, or Gr. ?. See Pro.]
   A prefix signifying before, in front, forth, for, in behalf
   of, in place of, according to; as, propose, to place before;
   proceed, to go before or forward; project, to throw forward;
   prologue, part spoken before (the main piece); propel,
   prognathous; provide, to look out for; pronoun, a word
   instead of a noun; proconsul, a person acting in place of a
   consul; proportion, arrangement according to parts.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

81 Moby Thesaurus words for "pro":
   Admirable Crichton, adept, advocating, all for, approving,
   argument, argumentum, artisan, artist, attache, authority, aye,
   backing, case, con, connaisseur, connoisseur, cons, consideration,
   consultant, cordon bleu, crack shot, craftsman, dead shot,
   diplomat, diplomatist, doyen, elder statesman, elenchus,
   experienced hand, expert, expert consultant, favorable, favoring,
   for, functional, gownsman, graduate, handy man, ignoratio elenchi,
   in favor of, industrial, interest, journeyman, marksman, master,
   nay, no, no slouch, official, old pro, plaidoyer, plea, pleading,
   politician, professional, professor, proficient, pros,
   pros and cons, reason, refutation, savant, seasoned professional,
   shark, sharp, side, special pleading, statesman, supporting,
   talking point, technical, technical adviser, technician,
   the affirmative, the negative, vocational, well-disposed,
   well-inclined, whiz, with



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

PRO
       Precision RISC Organization (org.)


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

PRO. A Latin proposition signifying `for.' As to its effects in contracts,
vide Plowd. 412.