It's about smiling. Ear-to-ear smile or grin is when you have a very broad and generous smile. Such a smile when each corner of your mouth is by each of your ears.
by Mr. Peagram March 08, 2012
by B-ri Myrders June 25, 2010
Man, that gerrrl be cheesin' from ear to ear
by The Chow Man October 21, 2004