Looking at terminology to use in the essay, you may point to a distinction between "cultural traditions" and "individual expectations". Mersault defies both, but is, perhaps, most conspiciously lacking in fulfilling the expectations placed upon him as an individual.
The traditions of the culture at large are carried out regardless of Mersault's will and his defiance. This, perhaps, is one of the central conflicts of the novel - cultural traditions make demands upon individuals without consideration for individuals who may disagree. The funeral happens. The trial happens. Mersault would have chosen to skip both, probably, and get right to the result - the burial and the guillotine.
Since you ask what jargon to use, I will focus on that. First of all, your thesis statement should clearly state your position. You mention theme. Theme is definitely a term you need to use, but you should also develop the theme with other jargon realted to theme. Characterization is a term that's important here. So is setting. I would also describe specific literary devices related to the idea of tradition and how it's explored.
L'Estrange can be translated as "The Stranger," "The Outsider," or "The Alien (or Foreigner)" all of whom are individuals who oppose tradition.
Meursault opposes tradition in the following ways:
- He refuses to cry at his mother's funeral (instead, he smokes and falls asleep)
- He does not show outward signs of grief or mourning after his mother's death (instead, he goes to the beach and has sex with Marie)
- He refuses to jump at the job promotion that his boss lays in his lap (he hates work)
- He shows no guilt over shooting the Arab
- He does not make attempt to seek an engagement to Marie (even though she makes overt attempts for him to)
- He does not believe in God or go to church or observe the Sabbath
- He does not confess to the Chaplain before his death
- He wants an angry mob at his public execution
So, Meursault hates traditional cultures: the culture of death, the culture of the church, the culture of the workplace, the culture of the judicial system. He defies all their traditions, beliefs, and mores in attempts to assert his perfervid individualism and stress the absurd nature of the universe.