An "intentional radiator" is a physical antenna. An "unintentional radiator" is something that radiates, but is not intended to. For instance, a battery, a trace, a display, a CPU, a charging cable, an accessory cable, etc, are not intended to radiate, but most of the time they do (unless properly designed to abate any radiators).
An intentional radiator can usually be "wholely contained", like removing the antenna and transmitting into a matched dissipating load. When this is done, the unintentional radiators will dominate the output spectrum. Hopefully, they will express themselves at levels below the FCC limits. If not, considerable effort might be needed to mitigate the radiators.
In my experience, the unintentional radiators are very difficult to mitigate, because the underlining design is "flawed". When they become apparent late in the design cycle, changes in the offending design is very much frowned upon and management pressures engineering for "quick fixes".