As far as the Canadian government is concerned, Raed Jaser and Chiheb Esseghaier are terrorists. The pair allegedly plotted to derail a passenger train en route between Toronto and New York.

Jaser and Esseghaier are now in trial in Ontario, facing multiple terrorism-related charges.

By contrast, Lindsay Kanittha Souvannarath and Randall Steven Shepherd are not considered terrorists.

The pair was arrested at the Halifax Stanfield International Airport last week and are facing charges of conspiracy to commit murder. They're due to make their first court appearance in Halifax this week.

Police allege Souvannarath and Shepherd — from Geneva, Ill. and Halifax, respectively — were part of a plot to shoot people at the Halifax Shopping Centre on Valentine's Day.

"The attack does not appear to have been culturally motivated, therefore not linked to terrorism," federal Justice Minister Peter MacKay said Saturday in his first public comments on the alleged plot.

MacKay dismissed any suggestion this case could be terrorism, describing the group accused of planning to attack the mall as "murderous misfits."

So what is terrorism?

Definition of terrorism

The Oxford English Dictionary defines it as the "unofficial or unauthorized use of violence and intimidation in the pursuit of political aims."

The Criminal Code includes a lengthy list of crimes in this category, including hijacking, endangering aircraft, taking hostages, attacking diplomats and trying to steal or tamper with nuclear material.

The Criminal Code goes on to identify terrorism as an offence that is committed "in whole or in part for a political, religious or ideological purpose, objective or cause."

Terrorism, according to the Criminal Code, can be used to influence someone to do something they don't want to do or to stop them from doing something they have been doing.

Motivation is at the heart of the matter. And right now, it's not clear what might have motivated Souvannarath and Shepherd to allegedly plan an attack on a mall.

A third suspect, 19-year-old James Gamble, killed himself as police closed in on his Timberlea home. His online posts included ones that read "Valentine's Day it's going down" and "What doesn't kill me might make me kill you."

Questions on motivation

While dark and vaguely threatening, the posts don't shed any light on motive. And on the surface, they don't appear to meet the Criminal Code test for terrorism.

Jaser and Esseghaier,  the two accused of plotting to derail a train, do appear to meet the test for at least the laying of terrorism charges.

Their trial has heard how Esseghaier talked about having received training, including how to recruit people to carry out terror plots such as attacking the train, poisoning soldiers on a military base, or attacking non-religious Muslims.

More details on what motivated Gamble, Souvannarath and Shepherd — and how police will justify the charges against the latter two — will come out as the case moves through the courts.

Shepherd and Souvannarath are scheduled to appear in a Halifax courtroom Tuesday morning.