A grin given by the grinner to show or perhaps hide an inside thought or observation of their surroundings. The grin is usually obvious and not containable but more likely the grinner does not want to contain the grin therefore getting their point across without speaking. Sometimes you just can't say things with words so don a shit grin instead!
"Every time my boyfriend looks at my ass he dons a shit grin."
by timmyg July 03, 2012