The Collaborative International Dictionary of English v.0.48:

Courteous \Cour"te*ous\ (k?r"t?-?s; 277), a. [OE. cortais,
   corteis, cortois, rarely corteous, OF. corties, corteis, F.
   courtois. See Court.]
   Of courtlike manners; pertaining to, or expressive of,
   courtesy; characterized by courtesy; civil; obliging; well
   bred; polite; affable; complaisant.
   [1913 Webster]

         A patient and courteous bearing.         --Prescott.
   [1913 Webster]

         His behavior toward his people is grave and courteous.
                                                  --Fuller.
   [1913 Webster]

WordNet (r) 3.0 (2006):

courteous
    adj 1: exhibiting courtesy and politeness; "a nice gesture"
           [syn: courteous, gracious, nice]
    2: characterized by courtesy and gracious good manners; "if a
       man be gracious and courteous to strangers it shows he is a
       citizen of the world"-Francis Bacon [ant: discourteous]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "courteous":
   accommodating, affable, agreeable, amiable, attentive, cap in hand,
   ceremonious, civil, civilized, clubbable, clubbish, clubby,
   communicative, companionable, companionate, compatible,
   complaisant, congenial, considerate, courtly, decorous,
   deferential, diplomatic, dutiful, fair, fit for society,
   fond of society, friendly, genial, genteel, gentlemanly, graceful,
   gracious, gregarious, honorific, hospitable, ladylike, mannerly,
   obliging, polished, polite, proper, regardful, respectful,
   sociable, social, social-minded, solicitous, tactful, thoughtful,
   urbane, well-behaved, well-bred, well-mannered