on (one's) ass adj 1. to focus negative attention on a person, e.g. by insulting, berating, or generally harassing someone. ("That guy was on your ass last night!") ("Get off my ass!") Submitted by Lance Spotted Elk, Boston, Mass. USA, 26-04-1998. 2. to drive a car such that it's extremely close to the car ahead. ("I wish that car would get off my ass.")
ON ASS
Meaning of ON ASS in English
Slang English vocab. Английский сленговый словарь. 2012