Longman Dictionary of Contemporary English
Wiktionary
n. A special piece of clothing worn by soldiers to protect them from shrapnel and grenade fragments, other non-direct fire and battlefield debris. Sometimes used informally to connote any of the various forms of a bullet-proof vest.
Wikipedia
thumb|300px|The two components of an obsolete British military flak vest. On the left, the nylon vest. On the right, the several layers of ballistic nylon that provide the actual protection
A flak jacket or flak vest is a form of body armor designed to provide protection from case fragments ("frag") from high explosive weaponry, such as anti-aircraft artillery ("flak" a German contraction for "Fliegerabwehrkanone" (aircraft-defense gun)), grenades, some round shot used in shotguns and land mines and other lower-velocity projectiles. It is not designed to protect against bullets fired from small-arms such as rifles or handguns. However, certain flak jackets are able to sustain certain gunshots, dependent on the armor, the gun, and the distance that the bullet has travelled.
The term "flak jacket" is often colloquially applied to newer body armor featuring protection against small arms projectiles, but the original usage predated the existence of functional bulletproof vests and the two are not interchangeable in performance.
Usage examples of "flak jacket".
He was wearing his helmet and flak jacket and had the rolled-up hammock strapped to his cartridge belt.
Binnie stowed his out of sight inside his flak jacket and we each took a Sterling from Cork's armoury.
The pulse had struck him in the left side of the left buttock, below the flak jacket, destroying the left pelvis.
Ferguson said as he stood at the rail wearing the third flak jacket, a Browning in one hand.
Sherwood shouted at a blue-cap with FBI printed in yellow on the front of his flak jacket: ‘.
The American dodged backwards desperately, the quarters too close to get off a shot, but the spearblade slid along his side, slicing open his flak jacket.
With his riot helmet and dark glasses and his tail tucked down inside his flak jacket, nobody spared him a glance.
She knew she couldn't pull it out-the blade and the shock-absorbent gel of the flak jacket were probably the only thing keeping the wound even partially sealed.
Since the kid had on a flak jacket, it was going to have to be a head shot, right into those eyes that looked like Hellena's, that smile that had flashed so easily just two minutes before.
He stripped off the flight engineer's flak jacket, oblivious to the screech of pain that it caused from the wrecked shoulder.
His face was dark with stubble, and he wore a flak jacket over a grimy, sweat-stained shirt.
He had been sleeping in his flak jacket and had made Anna, Grady, and Jason wear them fully clothed to bed.