Why did the shares of Hindustan Unilever (HUL) slip so sharply on 07 May during trading hours?

You are right that the shares of Hindustan Unilever slipped 5% to Rs.1902 on 07 May. This was after Glaxo offloaded its stake in HUL, allotted to them as consideration for sale of the consumer business to Unilever. According to the term sheet, over 13.30 crore shares, representing 5.7% of the total equity capital was offered for sale through the special block window. The deal was worth over Rs.25,000 crore. The entire lot of 13.3 crore shares changed hands on the BSE and NSE combined. While the seller was Glaxo, the buyer identity was not known immediately. Since the deal was announced, HUL has lost nearly 25% from its peak price touched on April 08 of Rs.2614. However, many analysts do consider this an opportunity moment to enter the stock all over again as the overhang of the Glaxo sale is finally over. Post the merger the ownership of Unilever PLC in HUL reduced from 67.19% to 61.90%.