To scribble is to write something quickly and sloppily. You can also call someone's handwriting, if it's hard to read, a scribble.

Pronunciation: /'skrɪbl/
English description: write carelessly
Synonyms: scrawl
Chinese Translation: 乱涂(luan4 tu2)
Spanish Translation: garabatear
ORIGIN: Have you ever made a note of something very quickly, and then later when you tried to read it, you couldn't? That's a scribble. People scribble when they need to write fast. The problem with scribbling—-making a scribble-—is that it’s hard to read. Some people have handwriting that is always hard to read: you can call poor handwriting a scribble. Doctors are famous for their scribbles. The Latin root is scribere, "to write."

EXAMPLE SENTENCE:

At some point Lord and Miller had scribbled down an idea for an end-of-the-world comedy.
I was the daughter who wasn’t allowed to touch the coloring books because I just scribbled all over them.

*New word description, story and part of "EXAMPLE SENTENCE" are cited in Vocabulary.com