‖n. [ L., flight of steps. ] (Zool.) Any one of numerous species of marine gastropods of the genus Scalaria, or family Scalaridae, having elongated spiral turreted shells, with rounded whorls, usually crossed by ribs or varices. The color is generally white or pale. Called also ladder shell, and wentletrap. See Ptenoglossa, and Wentletrap. [ 1913 Webster ]

n. [ It., contr. fr. malaaria bad air. See Malice, and Air. ] 1. Air infected with some noxious substance capable of engendering disease; esp., an unhealthy exhalation from certain soils, as marshy or wet lands, producing fevers; miasma. [ Archaic ] [ 1913 Webster ]

☞ The morbific agent in malaria is supposed by some to be a vegetable microbe or its spores, and by others to be a very minute animal blood parasite (an infusorian). [ 1913 Webster ]

2. (Med.) A human disease caused by infection of red blood cells by a protozoan of the genus Plasmodium, giving rise to fever and chills and many other symptoms, characterized by their tendency to recur at definite and usually uniform intervals. The protozoal infection is usually transmitted from another infected individual by the bite of an Anopheles mosquito. [ 1913 Webster +PJC ]

n. A mosquito that transmits the malaria parasite; it is most commonly the Anopheles mosquito. [ WordNet 1.5 ]

. Any of several minute protozoans of the genus Plasmodium (syn. Haematozoon) which in their adult condition live in the tissues of mosquitoes of the genus Anopheles (which see) and when transferred to the blood of man, by the bite of the mosquito, produce malaria. The young parasites, or sporozoites, enter the red blood corpuscles, growing at their expense, undergoing sporulation, and finally destroying the corpuscles, thus liberating in the blood plasma an immense number of small spores called merozoites. An indefinite but not ultimated number of such generations may follow, but if meanwhile the host is bitten by a mosquito, the parasites develop into gametes in the stomach of the insect. These conjugate, the zygote thus produced divides, forming spores, and eventually sporozoites, which, penetrating to the salivary glands of the mosquito, may be introduced into a new host. The attacks of the disease coincide with the dissolution of the corpuscles and liberation of the spores and products of growth of the parasites into the blood plasma. Several species of the parasite are distinguished, as Plasmodium vivax, producing tertian malaria; Plasmodium malariae, quartan malaria; and Plasmodium (subgenus Laverania) falciferum, the malarial fever of summer and autumn common in the tropics. [ Webster 1913 Suppl. ]

n. [ It., contr. fr. malaaria bad air. See Malice, and Air. ] 1. Air infected with some noxious substance capable of engendering disease; esp., an unhealthy exhalation from certain soils, as marshy or wet lands, producing fevers; miasma. [ Archaic ] [ 1913 Webster ]

☞ The morbific agent in malaria is supposed by some to be a vegetable microbe or its spores, and by others to be a very minute animal blood parasite (an infusorian). [ 1913 Webster ]

2. (Med.) A human disease caused by infection of red blood cells by a protozoan of the genus Plasmodium, giving rise to fever and chills and many other symptoms, characterized by their tendency to recur at definite and usually uniform intervals. The protozoal infection is usually transmitted from another infected individual by the bite of an Anopheles mosquito. [ 1913 Webster +PJC ]

n. A mosquito that transmits the malaria parasite; it is most commonly the Anopheles mosquito. [ WordNet 1.5 ]

. Any of several minute protozoans of the genus Plasmodium (syn. Haematozoon) which in their adult condition live in the tissues of mosquitoes of the genus Anopheles (which see) and when transferred to the blood of man, by the bite of the mosquito, produce malaria. The young parasites, or sporozoites, enter the red blood corpuscles, growing at their expense, undergoing sporulation, and finally destroying the corpuscles, thus liberating in the blood plasma an immense number of small spores called merozoites. An indefinite but not ultimated number of such generations may follow, but if meanwhile the host is bitten by a mosquito, the parasites develop into gametes in the stomach of the insect. These conjugate, the zygote thus produced divides, forming spores, and eventually sporozoites, which, penetrating to the salivary glands of the mosquito, may be introduced into a new host. The attacks of the disease coincide with the dissolution of the corpuscles and liberation of the spores and products of growth of the parasites into the blood plasma. Several species of the parasite are distinguished, as Plasmodium vivax, producing tertian malaria; Plasmodium malariae, quartan malaria; and Plasmodium (subgenus Laverania) falciferum, the malarial fever of summer and autumn common in the tropics. [ Webster 1913 Suppl. ]