What does "tar and feather" mean?

Criticize severely, punish, as in The traditionalists often want to tar and feather those who don't conform. This expression alludes to a former brutal punishment in which a person was smeared with tar and covered with feathers, which then stuck. It was first used as a punishment for theft in the English navy, recorded in the Ordinance of Richard I in 1189, and by the mid-1700s had become mob practice. The figurative usage dates from the mid-1800s.