The Collaborative International Dictionary of English v.0.48:

Pulmonata \Pul`mo*na"ta\, n. pl. [NL., from L. pulmo, -onis, a
   lung.] (Zool.)
   An extensive division, or sub-class, of hermaphrodite
   gastropods, in which the mantle cavity is modified into an
   air-breathing organ, as in Helix, or land snails, Limax, or
   garden slugs, and many pond snails, as Limn[ae]a and
   Planorbis.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Pulmonata
    n 1: large order of gastropods usually breathing by means of a
         lung-like sac comprising most land snails and slugs and
         many freshwater snails [syn: Pulmonata, order
         Pulmonata]