Merriam-Webster's Advanced Learner's Dictionary:
notebook
note·book /ˈnoʊtˌbʊk/ noun, pl -books [count]
1 : a book with blank pages that is used for writing notes
• Take out your notebook and write down some of your ideas.
• She kept a notebook for her poetry.
2 : a small computer that is designed to be easily carried - called also notebook computer,