The term 'uniformitarianism' is normally used rather than 'actualism'. Originally, 'uniformitarianism' was used to refer to gradualism but it is now it refers to actualism.
Creationists tend to use the term 'uniformitarianism' as if it still meant gradualism and then claim that geologists switch from that to catastrophism when it suits them. This is inaccurate.
A brief page on actualism in the WikiBook Historical Geology.
Actualism (Modern Uniformitarianism) and its Assumptions
Mr. Oard's Confused and Outdated Beliefs on Actualism
The Authors of Oard and Reed (2009) Still Confuse Actualism with Lyell Uniformitarianism
A Geologist's Biases are Your Biases
Essays by geochemist Kevin R. Henke on his Responding to Creationism website.