There are several synonyms for the phrase "do a disappearing act," which means to suddenly leave a place or situation without notice. Some alternatives include "make oneself scarce," "vanish into thin air," "slip away," "drop off the radar," "fade into the background," "take a powder," and "pull a Houdini." These phrases all convey the idea of someone leaving in a sudden and unexpected manner, often without explaining their reasons for doing so. Whether used in casual conversation or in more formal writing, these synonyms can add variety and interest to one's language and help convey a specific tone or mood.