Other forms: grinning, grins, grinned
A grin is a wide smile with the teeth showing, and to grin is to wear one. The face of a child handed an ice cream, or a friend across the table who knows exactly what you did last night.
Grin is broader and more open than smile, and it carries mischief as easily as joy: a sheepish grin, a wicked grin, grinning from ear to ear. It works as a noun too — a huge grin spread across his face. It takes AT for the person you aim it at (she grinned at me over her cup), and it doubles the n before endings: grinned, grinning. The phrase worth learning whole is grin and bear it, which means taking something unpleasant without a word of complaint.
1verbgrinTo smile widely, showing your teeth.
“He grinned when he saw the size of the cake.”
2nounwideA wide smile that shows the teeth.
“She answered with a grin and said nothing at all.”
Too few real examples of this word to estimate which sense is commonest.
grin is a kind of smile.
Grin runs back through Middle English grinnen to Old English grennian and Proto-Germanic granjōną, and its nearest English relative is groan. Middle High German grennen meant to mutter or complain, and Danish grine still means to show your teeth. Baring the teeth came first; the happiness was added later.
Proto-Germanic
*granjōną
Proto-West Germanic
*grannjōn
Old English
grennian
Middle English
grinnen
English, today
grin
From Middle English grinnen, from Old English grennian, from Proto-West Germanic grannjōn, from Proto-Germanic granjōną. Related to groan. Compare to Middle High German grennen (“to mutter, complain”) and Danish grine (“to show one's teeth, to laugh”)
Etymology from Wiktionary, CC BY-SA