1. [adj]  drawing blood from the body of another; "a plague of bloodsucking insects"
2. [adj]  of plants or persons; having the nature or habits of a parasite or leech; living off another; "a wealthy class parasitic upon the labor of the masses"; "parasitic vines that strangle the trees"; "bloodsucking blackmailer"; "his indolent leechlike existence"

BLOODSUCKING is a 12 letter word that starts with B.