Williams, who faces fellow American Alison Riske in the quarter-finals on Tuesday as she looks to win her 24th Grand Slam title, has yet to comment on the fine.
The incident occurred during a practice session in the build up to the competition.
Fabio Fognini was also fined $3,000 (£2,396) for unsportsmanlike conduct after a rant during his third round defeat to Tennys Sandgren.
The Italian had said he hoped a "bomb" would explode at the All England Club.
Nick Kyrgios was fined $8,000 (£6,406) in total from separate unsportsmanlike incidents in his first and second rounds.
The fiery Australian lost to Rafael Nadal in the second round.
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