1. [n]  a light two-wheeled vehicle for one person; drawn by one horse
2. [adj]  sullen or moody

SULKY is a 5 letter word that starts with S.

1. \Sulk"y\, a. [Compar. {Sulkier}; superl. {Sulkiest}.] [See
   {Sulkiness}, and cf. {Sulky}, n.]
   Moodly silent; sullen; sour; obstinate; morose; splenetic.
   
   Syn: See {Sullen}.
   
   

2. \Sulk"y\, n.; pl. {Sulkies}. [From {Sulky}, a.; -- so
   called from the owner's desire of riding alone.]
   A light two-wheeled carriage for a single person.
   
   Note: Sulky is used adjectively in the names of several
         agricultural machines drawn by horses to denote that
         the machine is provided with wheels and a seat for the
         driver; as, sulky plow; sulky harrow; sulky rake, etc.