Wiktionary
n. The number of words in a passage of text.
Wikipedia
The word count is the number of words in a document or passage of text. Word counting may be needed when a text is required to stay within certain numbers of words. This may particularly be the case in academia, legal proceedings, journalism and advertising. Word count is commonly used by translators to determine the price for the translation job. Word counts may also be used to calculate measures of readability and to measure typing and reading speeds (usually in words per minute). When converting character counts to words, a measure of 5 or 6 characters to a word is generally used.
Usage examples of "word count".
For short fiction sent to magazines, you should also include an approximate word count.
If you use a computer, of course you can give a precise word count.
It is also a good idea to put a cover page over the manuscript and include the word count, title, name and address on that, as well.
If you do not use a computer, you can estimate the word count by picking ten or twelve lines at random from the story and averaging the word count in them.
It is very approximate, but if the editor has any quibbles he will get an accurate word count for himself.