Definition - What does Mouseover mean?
A mouseover is an event that occurs in a Graphical User Interface (GUI) when the mouse pointer is moved over an object on the screen such as an icon, a button, text box, or even the edge of a window. In some instances, the object responds to the mouseover by performing some kind of action or displays a tooltip containing a short description of the object.
A mouseover is also known as a mouse hover or simply hover.
Techopedia explains Mouseover
The response of an object to a mouseover event will depend on what the developer of the application specifies in the object’s corresponding event handler. To see how a link on this page responds to a mouseover event, move your mouse pointer over a link. In most cases, the underlying URL of the link will be displayed on the browser’s status bar.
It is important to note that the reaction of an object to a click event and a mouseover event are usually not the same. If you perform the two actions in rapid succession, you might fail to see how the object reacts to the mouseover event. For you to see an object’s reaction to a mouseover, you should hold the mouse pointer over the object for at least a second.