"Operative phrase" refers to the most important part of a sentence or statement. It is the key idea or phrase that carries the main meaning or purpose. Full definition
FCM's subtle but slippery operative phrase to place blame on «market forces» is misdirection. (remonline.com)
If healthy, though, is the operative phrase here as Golden State has been battered much of the second half of the season. (sbnation.com)
On a day that began with the San Francisco 49ers taking Utah quarterback Alex Smith (below) with the first pick and ended with the Denver Broncos gambling on former Ohio State running back Maurice Clarett at the end of the third round, the operative phrase was Hold that Tiger. (si.com)