The Collaborative International Dictionary of English v.0.48:

Slowworm \Slow"worm`\, n. [AS. sl[=a]wyrm; the first part is
   probably akin to sle['a]n to strike, the reptile being
   supposed to be very poisonous. See Slay, v. t., and
   Worm.] (Zool.)
   A lecertilian reptile; the blindworm.
   [1913 Webster]

WordNet (r) 3.0 (2006):

slowworm
    n 1: small burrowing legless European lizard with tiny eyes;
         popularly believed to be blind [syn: blindworm,
         slowworm, Anguis fragilis]