The event of an on-screen pointer being over an on-screen shape.(noun)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "mouseover" in a sentence
"An Australian teenager has become an overnight Internet celebrity for admitting that he was the mastermind behind the "mouseover" attack that led to Tuesday's Twitter ..."
"An Australian teenager has become an overnight Internet celebrity for admitting that he was the mastermind behind the "mouseover" attack that led to Tuesday's Twitter mayhem."
"It's called a "mouseover", and it requires FOUR LINES of coding, people."