This is the 3873rd most frequent Catalan word.
butxaca
Pocket.
In this sentence, 'butxaca' refers to the pocket of an item of clothing used to hold small objects.
Va posar les claus a la butxaca.
He put the keys in the pocket.
Here, 'butxaca' describes the size of the book, indicating it is small and portable, as a 'pocket-sized' item.
Aquest llibre és de butxaca, pràctic per viatjar.
This book is pocket-sized, practical for traveling.
In this context, 'butxaca' is idiomatic, referring to affordability or being within one's financial capability.