Source : Webster's Revised Unabridged Dictionary (1913)

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.

   {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.

Pro \Pro\, adv.
   For, on, or in behalf of, the affirmative side; -- in
   contrast with {con}.

   {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.

Source : WordNet®

pro
     n 1: an athlete who plays for pay [syn: {professional}] [ant: {amateur}]
     2: an argument in favor of a proposal [ant: {con}]

pro
     adj : in favor of (an action or proposal etc.); "a pro vote" [ant:
            {anti}]

pro
     adv : on the affirmative side [ant: {con}]