What's the difference between begrime and begrimer?

Begrime

Definition:

• (v. t.) To soil with grime or dirt deeply impressed or rubbed in.

Example Sentences:

• (1) Often only one – and sometimes no – carriage door would open when they pulled into a station, and in summer they were “cooled” only by the methodical sweep of a begrimed metal fan that just pushed the sordid air about.
• (2) A Wall Street Journal editorialist fumed the program was “death by bicycle” and that the rows of Citi Bike racks “begrimed” the city.

Begrimer

Definition:

• (n.) One who, or that which, begrimes.

Example Sentences:

• (1) Often only one – and sometimes no – carriage door would open when they pulled into a station, and in summer they were “cooled” only by the methodical sweep of a begrimed metal fan that just pushed the sordid air about.
• (2) A Wall Street Journal editorialist fumed the program was “death by bicycle” and that the rows of Citi Bike racks “begrimed” the city.