When you are so excited or so angry that you lift your hand off the shift key to early and accidentally put a "1" at the end of your numerous exclamation marks.

Element of punctuation used by morons in place of the period, the full stop, that little dot near the L key. Note: one exclamation point is usually one too many. If you do plan to use more, please take care that you retain muscle control over the finger holding down the right-hand shift key. See also gay speak.