pointillism
Concise Oxford English Dictionary © 2008 Oxford University Press:
pointillism /ˈpwantɪlɪz(ə)m/
▶noun a technique of neo-Impressionist painting using tiny dots of various pure colours, which become blended in the viewer's eye.
– derivatives
pointillist noun & adjective,
pointillistic adjective.
pointillist noun & adjective,
pointillistic adjective.
– origin C19: from Fr. pointillisme, from pointiller ‘mark with dots’.
'pointillism' also found in these Oxford entries:

