Pump empty refers to a situation where a pump has run out of its contents and needs to be refilled. There are several synonyms that can be used in place of this phrase, such as depleted, drained, exhausted, and emptied out. These terms indicate that the pump has been used up and needs to be filled again. Other alternatives include evacuated, cleared out, voided, and purged, which suggest a more forceful removal of the contents from the pump. Regardless of which synonym is used, the implication is clear - the pump needs to be refilled in order to function properly.