1. Full-width at half-maximum in which the independent variable is time. Common abbreviationFDHM.2. Pertaining to the time interval during which a characteristic or property of a variable, such as the amplitude of a pulse, has a value greater than 50% of its maximum value. Synonym full-duration half-maximum. See also amplitude,  characteristic,  full-width at half-maximum,  independent variable,  pulse,  value,  variable.