WordNet sense 1 (digested with difficulty):

indigestible

WordNet sense 2 ((used pejoratively) out of fashion; old fashioned):

fogyish, mossy, stick-in-the-mud, moss-grown

WordNet sense 3 (not in accord with or not following current fashion):

unfashionable, unstylish

WordNet sense 4 (excessively conventional and unimaginative and hence dull):

stuffy

WordNet sense 5 (following accepted customs and proprieties):

conventional