lag verb
ADV. badly, seriously | behind She did well in her first year at school but then started to lag behind.
PREP. behind Britain still lags badly behind the rest of Europe on this.
PHRASES lag far/way/well behind (sb/sth) The Tories are still lagging way behind in the opinion polls.
You can also check other dicts: lag (English, 中文解释 ), wordnet sense, Collins Definition