Longman Dictionary of Contemporary English
Wiktionary
n. A military-style raincoat with a belt and deep pockets and often epaulettes.
WordNet
n. a military style raincoat; belted with deep pockets
Wikipedia
A trench coat or trenchcoat is a raincoat made of waterproof heavy-duty cotton gabardine drill, or leather, or poplin. It generally has a removable insulated lining, raglan sleeves, and the classic versions come in various lengths ranging from just above the ankles (the longest) to above the knee (the shortest). It was originally an item of clothing for Army officers (developed prior to the war but adapted for use in the trenches of the First World War, hence its name) and shows this influence in its styling.
Traditionally this garment is double-breasted with 10 front buttons, has wide lapels, a storm flap and pockets that button-close. The coat is belted at the waist with a self-belt, as well as having straps around the wrists that also buckle (to keep water from running down the forearm when using binoculars in the rain). The coat often has shoulder straps that button-close; those were a functional feature in a military context. The traditional color of a trench coat was khaki, although newer versions come in many colors.
Usage examples of "trench coat".
The man in the trench coat was reaching into his breast pocket too.
In downtown Rosslyn, Virginia, a man in a nice suit and a trench coat, wearing a neatly trimmed beard, and hair so short that his scalp almost showed through, emerged from a Metro station and walked up the street to a mailbox.
Now that he was out on the road, he fished the extinct butt of a fat stogie from the pocket of his trench coat and stoked it into life with a wooden safety match.
She set her purse on the dusty plank floor and quickly folded the raincoat over the rough wooden stool, hoping that the trench coat would shield the gown from any splinters.
After a moment, she unfastened the buttons and the trench coat's belt and stuffed the ends of the belt into the coat's pockets.
He slid his hand inside his coat, grabbed his Walther, and held it at the ready just inside his trench coat.
Smith unbuttoned his trench coat and sat alone at a small table in the corner, taking a long drink of his demi and eating a roast beef sandwich as he studied the Second Bureau's dossier on the Black Flame.
But on the back of a door, on a metal hook, there was a trench coat He took it out with him.
He opened his dark trench coat and slid the sword away into its scabbard.
A teenager in a ragged trench coat and tennis shoes peered through the glass at them: he was all by himself, like a guppie in a well-lit aquarium.
I was deathly tired, stumbling and staggering as much as running, blood soaking my tattered trench coat.