20th century political scientist and historian Robert Paxton was particularly interested in the defining elements of fascism. His studies involved an in-depth examination of Vichy France. Specifically, he was interested in how the government there became a willing collaborator with Nazi Germany.
In 2004, Paxton published The Anatomy of Fascism. This work spells out his particular definition of this ideology. While other political scientists and historians often view fascism in the abstract, Paxton sought to formulate a concrete definition.
Simply put, Paxton defines fascism as an application of political power that is deeply concerned with the notion of community decline. Fascists focus on the notion that their nation is subject to victimization by real and fabricated threats. This allows them to justify taking extreme and often violent actions against any opponents or critics. To achieve this, fascists form a strong national identity based on unity and purity of both thought and action. This requires that fascists build a strong sense of camaraderie; fascist governments often suppress individual identity. Loss of individuality leads to greater support of populist and nationalistic party-sanctioned violence. With widespread community support, the government can execute more programs aimed to cleanse society from within and expand its reach abroad. To achieve this, democratic ideals must be surrendered in the name of serving the greater good of the movement. Frequently, the regime is led by a strongman leader wearing the mantle of the national savior.
I have included a link to an online version of Paxton's book. I believe you will find an abbreviated version of Paxton's definition of fascism beginning on page 218.