WordNet sense 1 (distorted and unnatural in shape or size; abnormal and hideous):

grotesque, monstrous

WordNet sense 2 (displeasing to the senses):

ugly

WordNet sense 3 (lacking spontaneity; not natural):

forced, strained

WordNet sense 4 (artificially formal):

contrived

WordNet sense 5 (speaking or behaving in an artificial way to make an impression):

affected