Antonyms for Flat (opposite meaning)
WordNet sense 1 (raised in pitch by one chromatic semitone):
sharpWordNet sense 2 ((of a key) containing no sharps or flats; (of a note) being neither raised nor lowered by one chromatic semitone):
naturalWordNet sense 3 (having sharp differences between black and white):
contrastyWordNet sense 4 (not in a forthright manner):
indirectlyFrom the ODE community, based on WordNetadd/edit