The definition of a grin is a smile or expression of happiness.(noun)
A happy smile on your face is an example of a grin.
To grin is defined as to smile or make an expression that indicates great happiness.(verb)
When you feel very happy and you smile, this is an example of a situation where you grin.
See grin in Webster's New World College Dictionary
Origin: ME grennen < OE grennian, to gnash or bare the teeth, akin to OHG grennan, to mutter, Ger greinen, to weep
See grin in American Heritage Dictionary 4
verb grinned grinned, grin·ning, grins verb, intransitive
Origin: Middle English grennen, to grimace
Origin: , from Old English grennian.
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