planaria

noun

1. free-swimming mostly freshwater flatworms; popular in laboratory studies for the ability to regenerate lost parts

   noun.animal

   Synonyms planarian

   Source: WordNet 3.0

2. Any species of turbellarian worms belonging to <i>Planaria</i>, and many allied genera. The body is usually flat, thin, and smooth. Some species, in warm countries, are terrestrial.

   noun

   Source: webster1913