n 1  :  any of numerous bloodsucking arachnids that constitute the acarine superfamily Ixodoidea, are much larger than the closely related mites, attach themselves to warm-blooded vertebrates to feed, include important vectors of various infectious diseases of humans and lower animals, and although the immature larva has but six legs, may be readily distinguished from an insect by the complete lack of external segmentation  2  :  any of various usu. wingless parasitic dipteran flies (as the sheep ked) .
 
 
 
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