1. 
2. 
[syn: becoming, comely, comme il faut, decent, decorous, seemly]
The Collaborative International Dictionary of English v.0.48:
Decorous \Dec"or*ous\ (d[e^]k"[-o]r*[u^]s or d[-e]*k[=o]"r[u^]s;
   277), a. [L. dec[=o]rus, fr. decor comeliness, beauty; akin
   to decere. See Decent, and cf. Decorum.]
   Suitable to a character, or to the time, place, and occasion;
   marked with decorum; becoming; proper; seemly; befitting; as,
   a decorous speech; decorous behavior; a decorous dress for a
   judge.
   [1913 Webster]
         A decorous pretext the war.              --Motley.
   -- De*co"rous*ly, adv. -- De*co"rous*ness, n.
   [1913 Webster]
WordNet (r) 3.0 (2006):
decorous
    adj 1: characterized by propriety and dignity and good taste in
           manners and conduct; "the tete-a-tete was decorous in the
           extreme" [ant: indecorous, indelicate]
    2: according with custom or propriety; "her becoming modesty";
       "comely behavior"; "it is not comme il faut for a gentleman
       to be constantly asking for money"; "a decent burial";
       "seemly behavior" [syn: becoming, comely, comme il
       faut, decent, decorous, seemly]
Moby Thesaurus II by Grady Ward, 1.0:
98 Moby Thesaurus words for "decorous":
   Christian, accepted, according to Hoyle, acknowledged, admitted,
   appropriate, approved, au fait, becoming, befitting, being done,
   ceremonial, ceremonious, civil, civilized, comely, comme il faut,
   condign, conformable, conforming, conventional, correct, customary,
   de rigueur, decent, delicate, demure, dignified, done, due,
   earnest, elegant, felicitous, fit, fitting, formal, frowning,
   genteel, gentlemanly, good, grave, grim, grim-faced, grim-visaged,
   happy, hieratic, kosher, ladylike, liturgic, long-faced, mannerly,
   meet, modest, nice, normal, normative, orthodox, polished, polite,
   pompous, prim, proper, punctilious, received, recognized, refined,
   respectable, right, right and proper, righteous, rightful, rigid,
   ritual, ritualistic, sacerdotal, seasonable, sedate, seemly,
   serious, sober, sober-minded, sobersided, solemn, somber, staid,
   stately, stiff, stone-faced, straight-faced, stuffy, suitable,
   thoughtful, traditional, unsmiling, urbane, weighty, well-behaved,
   well-mannered