Synonyms for In style:

adj.

du jour (adjective)
stylish.
fashionable (adjective)
in vogue, modish.
prevailing (adjective)
fashionable.

n.

in style (noun)
fashionable, in vogue, modish, stylish, a la mode.

Other synonyms:

modish
modish.
Other relevant words:
fashionable.