A Quiz About Breaddhism
For example, your definition does not seem to apply to Theravada Buddhism.
Karma is the "intentional actions" one takes. The law of karma refers to the idea that one's karma will affect the "fruit of their karma", karmaphala. The cycle of rebirth, or reincarnation, is based on karmaphala. Your lot in life is based on your karmaphala, since the morally bad karma will carry on in rebirth and likewise for morally good karma.
Even interpreting the law of karma to mean "what goes around comes around" is an oversimplification. But, since we want people to get to type in the familiar word, the answer should be "The law of __________," where the blank is "karma".