Literary terms often have imposing names—even though the concept is not as complicated as it first seems. Asyndterm (or asyndeton) is one such term. The word looks like some calculus problem, but it simply means purposefully leaving out coordinating conjunctions (e.g., and) in related clauses.
You even know a famous example:
Veni, vidi, vici.
I came, I saw, I conquered.
Is this bad grammar? Technically yes, but that’s the beauty of it. If someone calls you on a missing and or but or or, you can tell them it’s asyndterm—if you can justify it.
In some instances, leaving out the conjunction gives balance and weight to each part. (It’s like those obsessive periods that show up in marketing now days.) Just make sure that you keep it rare and have a good reason for using it.