It means that for the bilingual or multilingual, his ability of using one specific language regresses with time due to the cease or reduction of use.

• 国外语蚀研究经历了七十多年的发展，现已形成一门独立的学科，其形成标志为1980年在美国宾夕法尼亚州大学召开的首届语言磨蚀研讨会。