When you cum in a girls mouth and it stretches across her teeth
Damn, that girl sure showed me her cumshield
A large pair of sunglasses. Built for style, but covering an area the size of a safety goggle. ie Paris hilton
"Adrianne's cum shield deflected Tysons errant pearl necklace harmlessy away."
An impervious bit of cloth, held over a young girl's pussy after cumming in it, to increase her chance of becoming pregnant.
When grandpa had cum over and over again in his little granddaughter, he put a pillow under her hips and a cum shield over her cunt--she was just having her period, so her parents wanted her to have a good chance of having his baby.