Whispering to Satan
Scholars have said that if a person dreams of whispering to Satan, it may indicate that they consult their enemies and support them against righteous people, though they will not be able to harm them. This is supported by the Quranic verse: "Private conversation is only from Satan to grieve those who have believed."
Per Ibn Sirin's Muntakhab al-Kalam fi Tafsir al-Ahlam