see Hyperintensity.

see High intensity focused ultrasound.

When describing most MRI sequences we refer to the shade of grey of tissues or fluid with the word intensity, leading to the following absolute terms:

high signal intensity = white

intermediate signal intensity = grey

low signal intensity = black

Often we refer to the appearance by relative terms:

hyperintense = brighter than the thing we are comparing it to

isointense = same brightness as the thing we are comparing it to

hypointense = darker than the thing we are comparing it to