The phrase "be up" can convey a variety of meanings, from being awake and alert to being available or functioning properly. Some synonyms for this phrase could include "awake," "alert," "ready," "operative," "functional," "available," "available for use," and "on hand." Depending on the context, other synonyms could include "up and about," "awake and aware," "on the go," "in operation," "in working order," "ready to go," and "in readiness." Using more descriptive language can help convey the intended meaning and add depth to written or spoken communications.