My first thought was indubitably, but that word is too fun to pronounce for it to be the most pretentious. I'll go with 'trivial', at least in the context of an academic explaining their work to someone outside or just starting to study their field.
Examples:
Person 1:"So you're a mathematician? Do you just do a lot of calculus and stuff like that then?"
Person 2: "Of course not, that type of math is trivial."
"Proof: this is trivial" (Particularly when this statement is formatted in the same way as real proofs and has a little box after it)