belabor

Short definition from Wiktionary

Verb

1. 1
   To labour about; labour over; to work hard upon; to ply diligently.
2. 2
   To beat or thump (someone) soundly.
3. 3
   To attack (someone) verbally.
4. 4
   To discuss or explain (something) excessively or repeatedly; to harp on or overelaborate.