Your body bleeding
internally (i.e. inside of it). If it is severe enough it can lead to damage all over the body. Can be caused by internal injuries (for example, a glass shard lodged in your lung, which would also cause a collapsed lung) or pathogens in the hemorrhagic fever category (ebola, dengue and
yellow fever for example) which cause your body to have clotting problems. If you think you're
internally bleeding, get to the hospital ASAP.
Person: I got bitten by a mosquito... I think I may have
yellow fever! I'm worried I'm
internally bleeding!
Friend of Person: We'll send you to the hospital real quick! Internal bleeding is extremely dangerous!
For
Urban dictionary, Internal bleeding is bleeding inside of your body.