You can achieve this in various known ways like Custom webpart, odifying XSLT, dding DataForm Webpart etc but one of the new and easiest ones that I saw on web is by using JS link.
With JS link property of a ListView you can control the rendering of items entirely. Take look at this example from LearningSharePoint.com which shows how easy it is to style announcements and modify the output as per your requirement.
You can also try few other Interesting Options that I found on the web -
Display Announcement Details in CallOuts on Hover Over of Item in SharePoint 2013
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