- Crawling with
- Creased
- Creating
- Creeping barrage
- Crib
- Cricket ball
- Crime
- Criq
- Crown and Anchor
- Crucifix Corner
- Crucifixion
- Cruiser
- Crummy
- Crump
- Crush
- Crusher
- Cubby hole, cubby hutch
- Cuckoo plane
- Cuffer
- Cuinchy
- Cully
- Cumshaw
- Cup and wad
- Cushy
- Cut a dido
- Cut out
- Cuthberts
- Cuxhaven
- Cyprus
- Czernowitz
- D.
- D.o.w.
- DCM
- DFC
- DRLS
- DSC
- DSM
- DSO
- Dabster
- Dado
- Dados
- Dag
- Dag up
- Dago
- Dags
- Daisy pushing
- Daisy roots (rhyming slang)
- Dandy
- Dar-es-Salaam
- Dar es Salaam (East Africa)
- Dardanelles
- Dark night patrol
- Dart
- Daty
- David
- David Lloyd George
- Day's pack
- Dazzle painting
- De-coder
- De-racks
- Dead Marine
- Debus
- Declaration of London
- Declaration of War
- Decoy ships
- Defeatist
- Defilade
- Degommy
- Dekko
- Delible
- Delousing chambers
- Demies
- Denmark
- Dennis
- Deolali tap
- Der tag day
- Derby
- Derzy
- Despatch 17 September 1914 (FM Sir John French)
- Despatch 23 December 1916 (FM Sir Douglas Haig)
- Despatch 7 September 1914 (FM Sir John French)
- Despatch 8 October 1914 (FM Sir John French)
- Deuce and ace (rhyming slang)
- Devil's Wood
- Dial
- Dicky dirt (rhyming slang)
- Dicky flurry
- Dicky flutter
- Dicky leave
- Dicky run
- Diddlum buck
- Died of wounds
- Diest (Belgium)
- Dig in
- Dig in the grave (rhyming slang)
- Dig out
- Digger
- Dimback
- Dinant (Belgium)
- Dinar
- Dingbat
- Dingy
- Dinkum
- Dinkum oil
- Dinky
- Dipped
- Disband
- Dispatches
- Distinguished Conduct Medal
- Distinguished Service Order
- Ditched
- Ditty box
- Division
- Dixie
- Dixmude
- Dizzy
- Do Svidanya
- Do an alley
- Do its damndest!
- Do one's bit
- Do one's nut
- Do the dirty
- Dobbs
- Dobra
- Dobying
- Dock
- Dodger
- Dog and Bonnet
- Dog biscuits
- Dog fight
- Dog watches
- Dogs
- Dogsbody
- Dog’s leg
- Doing it
- Don
- Don't bully the troops
- Done in
- Done to the wide
- Donkey’s breakfast
- Doo hicky
- Dooly
- Doornberg
- Dope
- Dora
- Dosinghem
- Dot
- Douane
- Dough
- Dough nuts
- Doughboys
- Doughcock
- Dover
- Dover Patrol
- Dragged
- Drina (river)
- Drowning flotilla
- Drum up
- Drummy
- Duala
- Duay
- Ducat
- Duck shoving
- Duckboard glide
- Duckboard harrier
- Duckboards
- Ducks disease
- Dud
- Duff
- Duffos
- Dufter
- Dug-out
- Duke of Fife (rhyming slang)
- Duke of York (rhyming slang)
- Dukla Pass
- Dullmajor
- Dum-Dum bullet
- Dumb insolence
- Dummy ships
- Dump
- Dun cow
- Dunayetz (river)
- Dunkirk
- Dunnage bag
- Dunsterforce
- Dustman
- Dusty boy
- Dutchman
- Dvina
- Dvinsk
- Dóbruja
- Dóbruja (Rumania)
- Düsseldorf
- EEF
- EFC
- EMSIB
- Eaps
- Earl Kitchener
- Earn
- Earthed
- East Africa
- East Prussia
- Eastern Front
- Eatables
- Echelon
- Edward Grey, 1st Viscount Grey of Fallodon
- Egg shells
- Eggs-a-cook
- Egypt
- El Kantara
- Elephant dug-out
- Embus
- Emma
- Emma Gees
- Emma Pips
- Emma Q
- Enfilade
- Entrenching
- Entrenching tool
- Erfs
- Erich von Falkenhayn
- Erk
- Ernest Troubridge
- Error of the day
- Ersatz
- Esma
- Espionage
- Esses
- Esses Emma
- Evacuate
- Ever since Adam was an oakum boy
- Expeditionary Force
- Exterior lines
- Eydtkuhnen
- Eye-witness
- Eyeties
- Eyewash
- FA
- FIDAC
- Fag issue
- Fairy light
- Falkland Islands
- Fan tan
- Fanny Adams
- Fao
- Fashy
- Fatigue duty
- Fatigues
- Fed up
- Feel out
- Felix
- Female tank
- Ferdinand Foch
- Fernleaves
- Festubert
- Fetch up
- Fiddler
- Fiddler's Green
- Field Army
- Field Marshal
- Field Marshal (rank)
- Field rats
- Finee
- Finger and thumb (rhyming slang)
- Fireworks
- First of the moon
- Five pence halfpenny
- Fixed bayonets
- Flag-wagging
- Flaming onions
- Flanders
- Flank
- Flanker
- Flap
- Flapper's delight
- Flat foot
- Flattening out
- Flesher
- Flight
- Flimp
- Flip
- Floaters
- Floating L's
- Flog
- Florin
- Florrie Ford
- Fluff
- Fly-catchers
- Fly boys
- Fly slicer
- Flying bedstead
- Flying kite
- Flying matinée
- Flying pig
- Focsani
- Focsani (Rumania)
- Fokker
- Follow the band
- Follow the drum
- Football
- Footslogger
- For it
- For the duration
- Force D
- Foreign Legion
- Forest of Argonne
- Forking the beam
- Forlorn hope
- Fort Troyon
- Four-flusher
- Four bag
- Four by two
- Fourth Army
- Fragmentation (weaponry)
- Franc
- Franc-tireurs
- France
- Frangine
- Frankenau
- Franz Ferdinand
- Fred Karno's Army
- Fred Karno's Navy
- Frederick Roberts, 1st Earl Roberts
- Free gangway
- Free tank
- Freiburg im Breisgau
- Frescati
- Friday while
- Friedrichshafen
- Frightfulness
- Frigo
- Fritz
- Frog and toad
- Frogging it
- Front
- Frontier
- Frying pans
- Full con
- Full pack
- Fundeni
- Fundeni (Rumania)
- Funk-hole
- Funky villas
- Furious joy
- Furphy