A character in the novel that I'm reading is described to have a fighter's chin. According to Wikipedia, it's a figurative term referring "to an ability to tolerate physical trauma to the chin or jaw without being knocked unconscious."
The way she's described makes it doubtful that it's being used for the figurative meaning. But I cannot find anything else on Google.
Can it mean a certain shape of a chin?
Here's the passage:
There was also fun in her, however. Her grey hair was gathered in a bun behind her, but there remained one sprightly forelock that flopped over her brow to the rhythm of her waddle. A hardy humour lit her brown eyes. Her mouth, set above a fighter's chin, seemed ready, given half a reason, to smile at any time.