The following comprises a list of words and phrases of the Armed Forces of the United Kingdom of Great Britain during the Great War, which also includes slang of the trenches and the Air Force; British and American service terms and expressions in everyday use; nicknames, sobriquets, and the titles of British and Commonwealth Regiments and their origins; and warfare in general. These words and phrases are contemporary to the war, which is reflected in the style and language used of the time, some of which may seem derogatory by today's standards. The following words and phrases have been transcribed from three primary sources (see contents). Feel free to help improve any of the entries in these lists.
- C3
- Cadet
- Cady
- Cag
- Cagnas
- Cain and Abel (rhyming slang)
- Cake walk
- Calm-Laylas
- Camel, The
- Camel Corps, The
- Camelier
- Camel-Wallah
- Camouflage
- Camp-followers
- Canard
- Canary
- Cane, The
- Cane, To
- Canned up
- Cannon fodder
- Canteen eggs
- Canteen medal
- Canteen stinker
- Canuck
- Cap badge
- Cape of Good Hope (rhyming slang)
- Capitulation
- Caprete
- Captain (rank)
- Carfindo
- Carl the caretaker's in charge
- Carney
- Carry on
- Cart
- Cartel
- Carving knife (rhyming slang)
- Casabianc
- Cashed in
- Castor oil artist
- Casualties of the Great War
- Category man
- Cats, The
- Cat stabber
- Cat walk, The
- Caterpillar
- Catsood
- Caulk
- Cavalry
- CB
- Ceiling
- Cells
- Cenotaph, The
- Centimes (Centimi, Centisimi)
- Central Flying School
- Central Powers
- Centre of Information
- Ceylon Planters' Rifle Corps
- Chain, Who pulled your
- Challenge ships
- Chance one's arm
- Chancer
- Char
- Char D'assaut
- Charley
- Charley Pope
- Charlie Noble
- Charming wife
- Chat
- Chat up, To
- Chat, Bombing the
- Chatham rats
- Chatty
- Chatty but happy
- Check
- Cheese it
- Cheerio!
- Chemist, The
- Chemozzle
- Cherry nobs
- Chest, Chuck a
- Chestnuts
- Chew the fat
- Chewed up, To be
- Chicken The
- Chicot
- China, Old
- Chinese attack
- Chinese Rolls Royce
- Chink
- Chinny
- Chin wag
- Chip in
- Chippy chap
- Chips
- Chit
- Choker
- Chokey
- Chow up
- Christians arise
- Christmas tree order, In
- Christmas truce, The
- Chuck
- Chuck a dummy
- Chuck one's hand in
- Chuck one's weight about
- Chuck up
- Chum, Long eared
- Chum, Long faced
- Chum, Long haired
- Chummy ship
- Chuprow (Chub-a-row, Chipperow)
- Church-by-hand
- Churchyard clock, As many faces as a
- Cinch
- Cinema
- Circus
- CIV
- Civvies
- Civvy kip
- Clack
- Clacker
- Clean and polish – We're winning the war
- Clean as a button stick
- Click
- Clickety click
- Client
- Clink
- Clinker
- Clobber
- Clod
- Clods
- Clout
- Clutching hand, The
- CMAR
- CMB
- CO
- Coal box
- Coal heaver
- Cockpit
- COD
- Code
- Coffee cooler
- Coffin nail
- Coggage (Coggidge)
- Coil up one's ropes
- Colco-Pari
- Cold feet
- Cold meat ticket
- Cold, To have someone
- Cold, To leave one
- Colonel (rank)
- Colour Sergeant (rank)
- Colours, The
- Colours, Bayonets and Drums in the City of London
- Columbus, The Knights of
- Column, To dodge the
- Column of Route
- Comb, The
- Combatant
- Come it (To come the old soldier; to come the old man)
- Come the double
- Comic business
- Comic cuts
- Coming the acid
- Commandant
- Commandeer
- Commander
- Commissariat
- Commission
- Commo
- Commodore
- Commonwealth of Nations
- Commonwealth War Graves Commission
- Communes of France
- Company (military unit)
- Company Quartermaster Sergeant (rank)
- Company Sergeant Major (rank)
- Compree
- Comrades of the mist
- Conchy
- Conk out
- Consolidate
- Conspicuous Gallantry Cross
- Consul
- Contemptibles, The Old
- Contour chasing
- Contraband of War
- Contract, Mess up the
- Convalesce
- Cooker
- Cook of the grot
- Cookhouse official
- Cook's tour
- Cooler, The
- Coop, The
- Coopetty coop
- Cooshy
- Cooter Goosht
- Coots, cooty
- Coppa dah
- Corned dog
- Cornstalks, The
- Corporal (rank)
- Corps (Army)
- Corpse ticket
- Cosh
- Cot, On the
- Coughing Clara
- Council of War
- Couple o' doorsteps
- Courrier de L'air
- Cow climbed up a hill
- Cow feed
- Crab
- Crab, A land
- Crab grenade
- Crackers, Get the
- Cramp one's style
- Crappo
- Crash
- Crash dive
- Crawl
- Crawling with
- Crawling on one's eyebrows
- Creased, To be
- Creating
- Creeping barrage
- Crib
- Cricket ball
- Crime
- Criq
- Crown, The
- Crown and Anchor
- Crucifix Corner
- Crucifixion
- Cruiser
- Crummy
- Crump
- Crush
- Crusher
- Crystal Palace, HMS
- Crystal Palace, The
- Cubby hole, cubby hutch
- Cuckoo plane
- Cuffer
- Cully
- Cumshaw
- Cup and wad
- Cushy
- Cut a dido
- Cut out
- Cuthberts
- Cuts, Have