Source : Webster's Revised Unabridged Dictionary (1913)

Buggy \Bug"gy\, a. [From {Bug}.]
   Infested or abounding with bugs.

Buggy \Bug"gy\, n.; pl. {Buggies}.
   1. A light one horse two-wheeled vehicle. [Eng.]

            Villebeck prevailed upon Flora to drive with him to
            the race in a buggy.                  --Beaconsfield.

   2. A light, four-wheeled vehicle, usually with one seat, and
      with or without a calash top. [U.S.]

   {Buggy cultivator}, a cultivator with a seat for the driver.
      

   {Buggy plow}, a plow, or set of plows, having a seat for the
      driver; -- called also {sulky plow}.

Source : WordNet®

buggy
     adj 1: informal or slang terms for mentally irregular; "it used to
            drive my husband balmy" [syn: {balmy}, {barmy}, {bats},
             {batty}, {bonkers}, {cracked}, {crackers}, {daft}, {dotty},
             {fruity}, {haywire}, {kooky}, {kookie}, {loco}, {loony},
             {loopy}, {nuts}, {nutty}, {round the bend}, {around
            the bend}, {wacky}, {whacky}]
     2: infested with bugs
     n : a small lightweight carriage; drawn by a single horse [syn:
         {roadster}]
     [also: {buggiest}, {buggier}]