Definition of "deerstalker"

Between 1997 and 2006, ownership of Glenfeshie passed between three Danish businessmen – and with it a self-destructive business model. Only by maintaining very high numbers of livestock could the flow of fee-paying deerstalkers armed with rifles be ensured, but because of the rising cost of gamekeepers and estate upkeep, Glenfeshie’s sporting operations were still making a loss.

2020 February 25, Christopher de Bellaigue, “The end of farming?”, in The Guardian‎

“Yes, sir, if that was the language of love, I'll eat my hat,” said the blood relation, alluding, I took it, to the beastly straw contraption in which she does her gardening, concerning which I can only say that it is almost as foul as Uncle Tom's Sherlock Holmes deerstalker, which has frightened more crows than any other lid in Worcestershire.

1960, P[elham] G[renville] Wodehouse, chapter XII, in Jeeves in the Offing, London: Herbert Jenkins

This is another area in which it's hard to tell the dude from the twitcher, as ratting caps and deerstalkers, flying helmets and even toppers are considered acceptably eccentric.

1980, Bill Oddie, Bill Oddie's Little Black Bird Book, page 61