As DaveSimmons noted, MultiSync monitors support a variety of resolutions and refresh rates. MultiSync is an NEC trademark for its multiscan monitors. NEC was the first to manufacture multiscan monitors, and like Xerox and photocopy, Multisync and multiscan are often used interchangeably.
In the "old days", monitors only ran one resolution. Today, nearly all consumer monitors are multiscan. I purchased an NEC 5FGP 17 inch MultiSync monitor in 1993. Cost me $1449 (USD). (At least the shipping was free!) Fortunately, prices have gone down.
Trinitron is a Sony trademark for its line of CRT's - the actual tube - not the rest of the monitor/TV.
On the other hand, MultiSync, NEC's trademark, has nothing to do with the actual CRT. MultiSync refers to switching circuitry, though NEC manufactures the entire monitor.