harp on (someone or something)
To persistently and annoyingly discuss or mention something. It was one mistake—why do you keep harping on it?
harp on someone or something
Fig. to keep talking or complaining about someone or something; to refer to someone or something again and again. I wish you would quit harping on Jeff all the time. He couldn't be all that bad. Stop harping on my mistakes and work on your own.
harp on
Dwell on; talk or write about to a tedious and excessive extent. For example, She kept harping on the fact that she had no household help at all. This expression is a shortening of harp on the same string, meaning "to play the same note over and over." It was first recorded in 1518.
harp on
v. To talk about something to an excessive and tedious degree; dwell on something: Every day my teacher harps on the importance of getting to class on time.