A small, brownish, rounded freshwater bivalve mollusc of the genus Pisidium (family Sphaeriidae or Pisidiidae), having fused siphons.
1950s; earliest use found in Science News.
英汉双解词典包含464360条英汉词条，基本涵盖了全部常用单词的翻译及用法，是英语学习的有利工具。