The resistance to twisting of a clubhead when impacted by an off-center hit. Golf clubs with high MOI measurements twist less and are therefore more stable, producing straighter shots on mishits than clubs with lower MOI.
The larger the clubhead, the higher the MOI. This is a primary advantage of oversize heads in irons as well as woods. The shape of a clubhead is also a factor, as positioning weight away from the center of gravity increases MOI. The USGA limits the amount of MOI in a driver to 6,000 grams per centimeter squared.
MOI is a key ingredient in the design of drivers, fairway woods, hybrids, irons and putters. Thomas Golf (www.thomasgolf.com) manufacturers a range of high-MOI clubs in each category.