It means Audit under other laws like Companies Act,Income Tax act, etc.
 
You can refer the below mentioned extract from the ‘Technical_Guide_on_GST_Audit’ by ICAI.
Combined reading of the Section 35(5), 44(2) along with the notified forms, give rise to two situations, namely, (a) entities not required to be audited under any other statute in which case audit has to be carried out in terms of Section 35(5) and reconciliation statement to be drawn under Section 44(2) duly certified and (b) entities that are required to be audited under any other statutes like the Companies Act, Income-tax Act, Co-operative Societies Act, etc., When the records of the entity are audited under any other statute, reconciliation statement can be drawn up by the same auditor, who will also certify the same or different auditor. Where the financials are audited (under any other law), then there is no requirement to conduct yet another audit of the same financials for GST purposes. GST audit exercise can proceed with the remainder of the exercise to prepare the reconciliation statement as required in Part A and certify as required in Part B. Where the financials are (somehow) not audited under any law, then these financials need to be audited for GST purposes apart from the exercise in Part A and Part B of GSTR 9C. Please note that there no guidance as to the ‘terms of reference’ for such a case. Given that this is a case that has come before a Chartered Accountant, his expertise will come to bear in providing a suitably audited financial statement to proceed with the Part A and Part B exercise in GSTR 9C.