Simple past tense and past participle of kill off.
Darian had killed off six Others while the rest had fled.
For instance, a Fungus epidemic is impossible unless the climatic conditions are such as to favor the dispersal and germination of the spores; and when plants are killed off owi~ig to the supersaturation of the soil with water, it is by no means obvious whether the excess of water and dissolved materials, or the exclusion of oxygen from the root-hairs, or the lowering of the temperature, or the accumulation of foul products of decomposition should be put into the foreground.
The preparations for the coronation of King James were interrupted by a severe visitation of the plague, which killed off as many as 30,578 persons, and it was not till March 25, 1604, that the king, the queen and Prince Henry passed triumphantly from the Tower to Westminster.
It is also probable that in a state of health organisms do gain entrance to the blood from time to time and are rapidly killed off.
This is chiefly to be regarded as an adaptation to surroundings, though the fact that the less virulent members of the bacterial species will be liable to be killed off also plays a part.;,Conversely, the virulence tends to diminish on cultivation on artificial media outside the body, especially in circumstances little favourable to growth.