Contract workers are "contractors". There is a clear deliverable and the worker produces it.

Consulting is the practice of engaging a business/org/lob to address a larger, less clear-cut problem. M&A is for M&A Consultants who specializes in acquiring and merging. Out of the merger may arise a unit of work to be "contracted out" in cases where timeline and capability are out of sync.

Can you consult under contract? Sure, but being a contractor doesn't automatically make you a Consultant.