The Collaborative International Dictionary of English v.0.48:
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.