The car was filthy when he returned it to me, and 'to cap it off' [='to top it off'], there was almost no fuel left in the tank.
a 'shower/bathing cap' [=a head covering that people wear to keep their hair dry when they are showering/swimming]
They may not like being called careless, but 'if the cap fits, wear it'. [=('US') 'if the shoe fits, wear it']
(..) under the convention will be based on three basic pillars: government, facilitative mechanism, and financial mechanism. In section , subsection F, it discusses cap-and-trade schemes and carbon taxes and the use of new and existing flexible carbon market mechanisms. These cap-and-trade (..)2009 Loose Change 9/11: An American Coup