What anime/manga would you say is the very definition of cute?
boku no pico
both the anime and the manga
You already posted it.
Any of the "pure moe" shows, they're all basically the same. Here's an episode of K-On:
This is bait.
Or is it too lewd?
Yotsuba, the manga
Also moe fucking sucks and there is nothing cute about a bunch of girls that look exactly alike and have hyper retardation and some rare form of tourette's that forces them to make retarded noises (chu, ugu, ehhhhhh!, etc.)
As much as I love Sakura Trick and K-ON, aesthetically speaking, Kiniro Mosaic has the cutest designs.