Vladimir Bukovsky in the Washington Post in 2005 wrote this article called Torture's Long Shadow, in which he explains what force feeding is:
The feeding pipe was thick, thicker than my nostril, and would not go in. Blood came gushing out of my nose and tears down my cheeks, but they kept pushing until the cartilages cracked. I guess I would have screamed if I could, but I could not with the pipe in my throat. I could breathe neither in nor out at first; I wheezed like a drowning man -- my lungs felt ready to burst. The doctor also seemed ready to burst into tears, but she kept shoving the pipe farther and farther down. Only when it reached my stomach could I resume breathing, carefully.This is what they're doing to the prisoners on hunger strike in Guantanamo Bay, held under suspicion of being terrorists, without being charged or tried, for the last 10 years:
There are 103 prisoners on hunger strike, with 31 being force-fed by military authorities and one in hospital. Since then, not a single prisoner has stopped their strike, and now 36 of the detainees are being force-fed to keep them alive, with five of them being hospitalised.