"Tokusatsu" is short for "Tokushuu Satsuei" which roughly translates to "Special Effects Photography".

In recent years however the term has come to be used in Japan to refer to features such as the Gamera series which trade specifically on their "SFX". These shows are called "Tokusatsu" becuase they rely on their effects and little else. There are numerous old school classics of Japanese tokusatsu including Hideaki Anno's personal favourite Ultraman. If you do enough digging you are sure to find some gems.