Wiktionary
n. (context computing slang English) In the computer security community, a skilled hacker who sometimes acts legally and in good will and sometimes not. They are a hybrid between "white hat" and "black hat" hackers. They hack for no personal gain, and do not have malicious intentions, but do commit crimes.
Usage examples of "gray hat".
The other had on khaki pants and a blue striped coat and a gray hat pulled down very low, hiding most of his face.
George couldn't see his face for the wide Spanish night-gray hat he wore.
Squint as much as he would, his gray hat and gray silk coat, embroidered with silver scrolls down the sleeves and collar, looked nothing like the helmet and armor he was used to.
Egwene was on the point of telling her about Theodrin and Faolain -- that should get some rise, and approval -- when she saw an olive-skinned woman ride past the open tent flaps looking lost in thought beneath the wide gray hat she wore to keep off the sun.
At one side, at the long table, he could see Goodwin's black head and gaunt brown face, and the woman's gray hat.
He grinned now, suddenly reached for the gray hat, swept it down in a low bow.
She snatched her gray hat and her new gray purse and gloves from her locker.
The old man reined up and stood for a moment immobile, head turned eastward toward the enemy, the gray hat on the horn of the saddle.
A pearl-gray hat and gray gloves and an ebony cane lay beside him on another chair.
She wore a perky gray hat with a veil, a gray traveling suit, and a white fur shoulder piece.
He towered over them in a velvet-collared coat, his big-brimmed soft gray hat pulled low on his head and flapping in the icy wind.