The term quorum call refers calling the roll in order to ascertain whether or not there is a quorum present.
U.S. Senate Definition
“A call of the roll to establish whether a quorum is present. If any senator 'suggests the absence of a quorum,' the presiding officer must direct the roll to be called. Often, a quorum call is terminated by unanimous consent before completion, which permits the Senate to use the quorum call to obtain a brief delay to work out some difficulty or await a senator's arrival.”