Canister. A German trench mortar shell filled with scraps of iron and nails. Tommy really has a great contempt for this little token of German affection and he uses the nails to hang his equipment on in the dugouts.
Canteen. A mess tin issued to Tommy, who, after dinner, generally forgets to wash it, and pinches his mates for tea in the evening.
"Carry on." Resume. Keep on with what you are doing. Go ahead.
"Carrying in." Machine gunners' term for taking guns, ammunition, etc., into front-line trench.
Caterpillar. Is not a bug, but the name given to a powerful engine used to haul the big guns over rough roads.
C.C.S. Casualty Clearing Station. A place where the doctors draw lots to see if Tommy is badly wounded enough to be sent to Blighty.
Chalk Pit. A white spot on a painted landscape used at the Machine Gunners' School to train would-be gunners in picking out distinctive objects in landscapes and guessing ranges.
Challenge. A question, "Who goes there?" thrown at an unknown moving object by a sentry in the darkness, who hopes that said moving object will answer, "Friend."
Char. A black poisonous brew which Tommy calls tea.
"Chevaux-de-frise." Barbed-wire defenses against cavalry.