Htcgg
htcgg is a member of the sprite structure. Its only actual use in the game's source code is in this block from the handling of the fall command:
if (!actor[vm.g_i].cgg-- || (sector[vm.g_sp->sectnum].floorstat&2)) { A_GetZLimits(vm.g_i); actor[vm.g_i].cgg = 3; }
TODO: What does "cgg" stand for? The source code does not say.