Definition - What does A Fortiori mean?
"A fortiori" is a legal term used to describe a conclusion that is stronger than the one that was originally thought of. Basically, it creates the same conclusion but is considered the primary way in which that is decided.
A popular example is in saying that if a person is not breathing, then a fortiori the person is dead; the fact that the person is dead is the strongest evidence to prove that the person is not breathing.
Justipedia explains A Fortiori
The use of a fortiori is meant to show that there is stronger evidence that can prove a fact (stronger than the initial evidence that was provided).