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