1. To speak softly, but loudly, with quite a bit of vibration to the vocal cords, not really caring about being overheard
2. The maximum volume of a whisper
3. When whispering just isn't loud enough

Short for ultimate bias. Typically used by fangirls and fanboys to describe their favourite celebrity amongst the many that they are fans of.

When a whisper just isn't not loud enough.

When someone thinks they are whispering, but do not realize they are doing even that loudly.