Wiktionary
word processing
n. The creation, input, editing and formatting of documents and other text using software on a computer
WordNet
word processing
n. rapid and efficient processing (storage and printing) of linguistic data for composition and editing
Usage examples of "word processing".
All that you see on your computer screen--your Tomb Raider, your digitized voice mail messages, faxes, and word processing documents written in thirty-seven different typefaces--is still, from the computer's point of view, just like telegrams, except much longer, and demanding of more arithmetic.
The fax was printed on a word processing application which opened up in yet another window.
If you load in a word processing program you can then use the computer to write a book.